Blockchain Papers

A curated list of blockchain-related academic papers. Papers with 🎓 have been peer-reviewed and presented in academic conferences.

Table of Contents

1. General
2. Consensus
3. Cryptography
4. Block generation and mining
5. Stake
6. Attacks
7. Wallets
8. Crime
9. Economics
10. Marketplaces and Trust
11. Privacy
12. Sidechains, Higher layer and Scalability
13. Payment Networks
14. Fungibility
15. Network
16. Smart Contracts
17. Formal Methods
18. Proof of work
19. DAG-based consensus mechanisms
20. Survey, Sociological & Anthropological
21. Applications
22. License

General

• Bitcoin: A Peer-to-Peer Electronic Cash System. Nakamoto S. '08.
• 🎓 SoK: Research Perspectives and Challenges for Bitcoin and Cryptocurrencies. Bonneau J, Miller A, Clark J, Narayanan A, Kroll JA, Felten EW. S&P '15.
• Bitcoin's Academic Pedigree. Narayanan A, Clark J. ACM Queue '17.
• 🎓A systematic literature review of blockchain-based applications: Current status, classification and open issues. Casino F, Dasaklis T, Patsakis C. T&I '18.

Consensus

• 🎓 The Bitcoin Backbone Protocol: Analysis and Applications. Garay J, Kiayias A, Leonardos N. EUROCRYPT '15.
• 🎓 The Bitcoin Backbone Protocol with Chains of Variable Difficulty. Garay J. Kiayias A, Leonardos N. '16. CRYPTO '17.
• 🎓 Analysis of the Blockchain Protocol in Asynchronous Networks. Pass R, Seeman L, shelat a. EUROCRYPT '17.
• On Trees, Chains and Fast Transactions in the Blockchain. Kiayias A, Panagiotakos G. '16.
• 🎓 "RSCoin": Centrally banked cryptocurrencies. Danezis G, Meiklejohn S. '15.
• Anonymous Byzantine Consensus from Moderately-Hard Puzzles: A Model for Bitcoin. Miller A, LaViola JJ Jr. '14.

Classic Consensus

• 🎓 The Byzantine Generals Problem. Lamport L, Shostak R., Pease M. '82. TOPLAS '82.
• 🎓 Consensus in the Presence of Partial Synchrony. Dwork S., Lynch N. '88. JACM '88.
• 🎓 Practical Byzantine Fault Tolerance. Castro M., Liskov B. '99. OSDI '99.
• 🎓 The part-time parliament. Lamport L. '00. TOCS '98.
• 🎓 Paxos Made Simple Lamport L. '00, ACM SIGACT News '01.

Cryptography

• On Bitcoin as a public randomness source. Bonneau J, Clark J, Goldfeder S. '15.
• Distributed Cryptography Based on the Proofs of Work. Andrychowicz M, and Dziembowski S. '14.
• Scalable, transparent, and post-quantum secure computational integrity. Ben-Sasson E, Bentov I, Horesh Y, Riabzev M. '18.
• 🎓 Bitcoin as a Transaction Ledger: A Composable Treatment. Badertscher C., Maurer U., Tschudi D., Zikas V. '19. CRYPTO '17.

Block generation and mining

• 🎓 Bootstrapping the Blockchain - Directly. Garay JA, Kiayias A, Leonardos N, Panagiotakos G. '16.
• Speed-Security Tradeoffs in Blockchain Protocols. Kiayias A, Panagiotakos G. '15.
• 🎓 "GHOST": Secure High-Rate Transaction Processing in Bitcoin. Sompolinsky Y, Zohar A. FC '15.
• 🎓 Inclusive Block Chain Protocols. Lewenberg Y, Sompolinsky Y, Zohar A. FC '15.
• 🎓 On the Security and Performance of Proof of Work Blockchains. Gervais A, Karame GO, Wüst K, Glykantzis V, Ritzdorf H, Capkun S. CCS '16.
• 🎓 Smartpool: Practical decentralized pooled mining. Luu L, Velner Y, Teutsch J, Saxena P. USENIX Security '17.

Stake

• 🎓 Ouroboros: A provably secure proof-of-stake blockchain protocol. Kiayias A, Russell A, David B, Oliynykov R. '16.
• 🎓 ALGORAND: The Efficient and Democratic Ledger. Micali S. '16.
• 🎓 "ByzCoin": Enhancing Bitcoin Security and Performance with Strong Consistency via Collective Signing. Kogias EK, Jovanovic P, Gailly N, Khoffi I, Gasser L, Ford B. USENIX '16.
• 🎓 Cryptocurrencies without Proof of Work. Bentov I, Gabizon A, Mizrahi A. FC '16.
• 🎓 Ouroboros Praos: An adaptively-secure, semi-synchronous proof-of-stake protocol. Bernardo D, Gazi P, Kiayias A, Russell A. Crypto '17.
• 🎓 Ouroboros Genesis: Composable Proof-of-Stake Blockchains with Dynamic Availability. Badertscher C, Gazi P, Kiayias A, Russell A, Zikas V. '18.
• 🎓 A Proof-of-Stake protocol for consensus on Bitcoin subchains. Bartoletti M, Lande S, & Podda A S. FC '17.
• 🎓 Snow White: Provably Secure Proofs of Stake.. Bentov I, Pass R, Shi E. FC '19.

Attacks

• 🎓 "Selfish Mining": Majority Is Not Enough: Bitcoin Mining Is Vulnerable. Eyal I, Sirer EG. FC '14.
• Theoretical Bitcoin Attacks with less than Half of the Computational Power. Bahack L. '13.
• 🎓 Optimal Selfish Mining Strategies in Bitcoin. Sapirshtein A, Sompolinsky Y, Zohar A. FC '16.
• 🎓 Refund attacks on Bitcoin’s Payment Protocol. McCorry P, Shahandashti S, Hao F. FC '16.
• Low-Resource Eclipse Attacks on Ethereum’s Peer-to-Peer Network. Marcus Y, Heilman E, Goldberg S. '18.
• 🎓 Hostile blockchain takeovers. Bonneau J. FC '18.

Wallets

• 🎓 Bitcoin Covenants. Möser M, Eyal I, Sirer EG. FC '16.
• 🎓 Enhancing Bitcoin Transactions with Covenants. O’Connor R, Piekarska M. FC '17.
• 🎓 Hierarchical deterministic Bitcoin wallets that tolerate key leakage. Gutoski G, Stebila D. FC '15.

Crime

• 🎓 ZombieCoin: Powering Next-Generation Botnets with Bitcoin. Ali ST, McCorry P, Lee PH, Hao F. FC '15.
• 🎓 The Bitcoin Brain Drain: A Short Paper on the Use and Abuse of Bitcoin Brain Wallets. Vasek M, Bonneau J, Castellucci R, Keith C, Moore T. FC '16.

Economics

• 🎓 On Bitcoin and Red Balloons. Babaioff M, Dobzinski S, Oren S, Zohar A. EC '12.
• 🎓 On the instability of Bitcoin without the block reward. Carlsten M, Kalodner H, Weinberg SM, Narayanan A. CCS '16.
• 🎓 The Economics of Bitcoin Mining or Bitcoin in the Presence of Adversaries. Kroll J, Davey I, Felten E. WEIS '13.
• 🎓 Trends, Tips, Tolls: A Longitudinal Study of Bitcoin Transaction Fees. Möser M, Böhme R. FC '15.
• 🎓 Why buy when you can rent? Bribery attacks on Bitcoin-style consensus. Bonneau J. FC '16.
• 🎓 Game-Theoretic Analysis of DDoS Attacks Against Bitcoin Mining Pools. Johnson B, Laszka A, Grossklags J, Vasek M, Moore T. FC '14.
• 🎓 When Bitcoin Mining Pools Run Dry A Game-Theoretic Analysis of the Long-Term Impact of Attacks Between Mining Pools. Laszka A, Johnson B, Grossklags J. FC '15.
• 🎓 Incentive Compatibility of Bitcoin Mining Pool Reward Functions. Schrijvers O, Bonneau J, Boneh D, Roughgarden T. FC '16.
• 🎓 When cryptocurrencies mine their own business. Teutsch J, Jain S, Saxena P. FC '16.
• 🎓 Incentivizing Blockchain Forks via Whale Transactions. Liao K, Katz J. FC '17.
• 🎓 Smart Contracts Make Bitcoin Mining Pools Vulnerable. Velner Y, Teutsch J, Luu L. FC '17.
• 🎓 Mixing Coins of Different Quality: A Game-Theoretic Approach. Abramova S, Schöttle P, Böhme R. FC '17.
• 🎓 Decentralized Prediction Market without Arbiters. Bentov I, Mizrahi A, Rosenfeld M. FC '17.
• 🎓 "Zeus": Analyzing Safety of Smart Contracts. Kalra S, Goel S, Dhawan M, Sharma S. NDSS '18.
• 🎓 How to Use Bitcoin to Design Fair Protocols. Bentov I, Kumaresan R. CRYPTO '14.
• 🎓 The Gap Game. Tsabary I., Eyal I. ACM CCS '18.

Marketplaces and Trust

• 🎓 Measuring the Longitudinal Evolution of the Online Anonymous Marketplace Ecosystem. Soska K, Christin N. USENIX '15.
• 🎓 Escrow protocols for cryptocurrencies: How to buy physical goods using Bitcoin. Goldfeder S, Bonneau J, Gennaro R, Narayanan A. FC '17.
• 🎓 Trust Is Risk: A Decentralized Financial Trust Platform. Thyfronitis Litos OS, Zindros D. FC '17.
• Trust in decentralized anonymous marketplaces. Zindros D. '15.
• Money as IOUs in social trust networks & a proposal for a decentralized currency network protocol. Fugger R. '04.
• The Ripple protocol consensus algorithm. Schwartz D, Youngs N, Britto A. '14.
• The stellar consensus protocol: A federated model for internet-level consensus. Mazières D. '15.
• 🎓 There’s No Free Lunch, Even Using Bitcoin: Tracking the Popularity and Profits of Virtual Currency Scams. Vasek M, Moore T. FC '15.
• 🎓 Challenges and Opportunities Associated with a Bitcoin-based Transaction Rating System. Vandervort D. FC '14.

Privacy

• 🎓 Zerocoin: Anonymous distributed e-cash from bitcoin. Miers I, Garman C, Green M, Rubin AD. S&P '13.
• 🎓 Zerocash: Decentralized anonymous payments from bitcoin. Sasson EB, Chiesa A, Garman C, Green M, Miers I, Tromer E, Virza M. S&P '14.
• "Monero": CryptoNote v2.0. Saberhagen N. '13?
• 🎓 Rational Zero: Economic Security for Zerocoin with Everlasting Anonymity. Garman C, Green M, Miers I, Rubin A. FC '14.
• Mixcoin: Anonymity for bitcoin with accountable mixes. Bonneau J, Narayanan A, Miller A, Clark J, Kroll JA, Felten EW. '14.
• TumbleBit: An untrusted Bitcoin-compatible anonymous payment hub. Heilman E, Alshenibr L, Baldimtsi F, Scafuro A, Goldberg S. '16.
• Blindly Signed Contracts: Anonymous On-Blockchain and Off-Blockchain Bitcoin Transactions. Heilman E, Baldimtsi F, Goldberg S. FC '16.
• 🎓 Coinshuffle: Practical decentralized coin mixing for bitcoin. Ruffing T, Moreno-Sanchez P, Kate A. ESORICS '14.
• 🎓 Quantitative analysis of the full bitcoin transaction graph. Ron D, Shamir A. FC '13.
• 🎓 How Did Dread Pirate Roberts Acquire and Protect His Bitcoin Wealth?. Ron D, Shamir A. FC '14.
• "MoneroLink": An Empirical Analysis of Linkability in the Monero Blockchain. Miller A, Möser M, Lee K, Narayanan A. '17.
• 🎓 Provisions: Privacy-preserving proofs of solvency for Bitcoin exchanges. Dagher GG, Bünz B, Bonneau J, Clark J, Boneh D. CCS '15.
• 🎓 Increasing Anonymity in Bitcoin. Saxena A, Misra J, Dhar A. FC '14.
• 🎓 Blindcoin Blinded, Accountable Mixes for Bitcoin. Valenta L, Rowan B. FC '15.
• 🎓 Hawk: The Blockchain Model of Cryptography and Privacy-Preserving Smart Contracts. Kosba A, Miller A, Shi E, Wen Z, Papamanthou C. SP '16
• 🎓 Could Network Information Facilitate Address Clustering in Bitcoin?. Neudecker T, Hartenstein H. FC '17.
• 🎓 Blind signatures for untraceable payments. Chaum D. CRYPTO '83.
• 🎓 Exchange Pattern Mining in the Bitcoin Transaction Directed Hypergraph. Ranshous S, Joslyn A, Kreyling S, Nowak K, Samatova N, West C, Winters C. FC '17.
• 🎓 Confidential Assets. Poelstra A, Back A, Friedenbach M, Maxwell G, Wuille P. FC '17.
• 🎓 Mixing Confidential Transactions: Comprehensive Transaction Privacy for Bitcoin. Ruffing T, Moreno-Sanchez P. FC '17.
• 🎓 Switch Commitments: A Safety Switch for Confidential Transactions. Ruffing T, Malavolta G. FC '17.
• 🎓 CoinParty: Secure Multi-Party Mixing of Bitcoins. Ziegeldorf, J.H., Grossmann, F., Henze, M., Inden, N. and Wehrle, K. CODASPY '15.
• Data-Driven De-Anonymization in Bitcoin. Nick J. Diss. ETH-Zürich, '15.
• 🎓 Deanonymisation of Clients in Bitcoin P2P Network. Biryukov A, Khovratovich D, Pustogarov I. CCS '14.
• 🎓 Transferable Anonymous Payments via TumbleBit in Permissioned Blockchains. Ferretti C, Leporati A, Mariot L, Nizzardo L. DLT '19.

Sidechains, Higher layer and Scalability

• Enabling Blockchain Innovations with Pegged Sidechains. Back A, Corallo M, Dashjr L, Friedenbach M, Maxwell G, Miller A, Poelstra A, Timón J, Wuille P. '14.
• 🎓 Proofs of Proofs of Work with Sublinear Complexity. Kiayias A, Lamprou N, Stouka AP. FC '16.
• 🎓 Bitcoin-NG: A Scalable Blockchain Protocol. Eyal I, Gencer AE, Sirer EG, Van Renesse R. USENIX '16.
• 🎓 On the Malleability of Bitcoin Transactions. Andrychowicz M, Dziembowski S, Malinowski D, Mazurek Ł. FC '15.
• 🎓 On Scaling Decentralized Blockchains. Croman K, Decker C, Eyal I, Gencer AE, Juels A, Kosba A, Miller A, Saxena P, Shi E, Sirer EG, Song D. FC '16.
• 🎓 "Elastico": A secure sharding protocol for open blockchains. Luu L, Narayanan V, Zheng C, Baweja K, Gilbert S, Saxena P. CCS '16.
• 🎓 Improving Authenticated Dynamic Dictionaries, with Applications to Cryptocurrencies. Reyzin L, Meshkov D, Chepurnoy A, Ivanov S. FC '17.
• 🎓 Service-Oriented Sharding for Blockchains. Gencer AE, Van Renesse R, Sirer EG. FC '17.
• Non-Interactive Proofs of Proof-of-Work. Kiayias A, Miller A, Zindros D. '17.
• 🎓 Proof-of-Stake Sidechains. Gaži P, Kiayias A, Zindros D. S&P '19.
• 🎓 Proof-of-Work Sidechains. Kiayias A, Zindros D. FC WTSC '19.
• FlyClient: Super-Light Clients for Cryptocurrencies. B Bünz, L Kiffer, L Luu, M Zamani. '19.
• PolyShard: Coded Sharding Achieves Linearly Scaling Efficiency and Security Simultaneously. Li S, Yu M, Avestimehr S, Kannan S, Viswanath P. '18.
• 🎓 ForkBase: An Efficient Storage Engine for Blockchain and Forkable Applications. Wang S, Dinh TT, Lin Q, Xie Z, Zhang M, Cai Q, Chen G, Ooi BC, Ruan P. PVLDB '18.

Payment Networks

• 🎓 A Fast and Scalable Payment Network with Bitcoin Duplex Micropayment Channels. Decker C, Wattenhofer R. SSS '15.
• The bitcoin lightning network: Scalable off-chain instant payments. Poon J, Dryja T. '15.
• "Deployable Lightning": Reaching The Ground With Lightning. Russell R. '15.
• 🎓 Teechan: Payment Channels Using Trusted Execution Environments. Lind J, Eyal I, Pietzuch P, Sirer EG. FC BITCOIN '17.
• 🎓 Revive: Rebalancing Off-Blockchain Payment Networks. Khalil, R., & Gervais, A. CCS '17.
• NOCUST – A Non-Custodial 2nd-Layer Financial Intermediary. Khalil R, Gervais, A. '18.
• Counterfactual: Generalized state channels. Coleman J, Horne L, Xuanji L. '18.
• Sprites and State Channels: Payment Networks that Go Faster than Lightning Miller A, Bentov I, Kumaresan R, Cordi C, McCorry P. '17.
• 🎓 Perun: Virtual payment hubs over cryptocurrencies Dziembowski S, Eckey L, Faust S, Malinowski D. IEEE S&P '19.
• 🎓 General State Channel Networks Dziembowski S, Faust S, Hostáková K. CCS '18.
• Bolt: Anonymous Payment Channels for Decentralized Currencies Green M, Miers I. '16.
• Flare: An Approach to Routing in Lightning Network. Prihodko P, Zhigulin S, Sahno M, Ostrovskiy A, Osuntokyn O. '16.
• On the Difficulty of Hiding the Balance of Lightning Network Channels. Herrera-Joancomartí J, Navarro-Arribas G, Ranchal-Pedrosa A, Pérez-Solà C, Garcia-Alfaro J. '19.
• Pisa: Arbitration Outsourcing for State Channels. McCorry P, Bakshi S, Bentov I, Meiklejohn S, Miller A. '18.
• 🎓 Concurrency and Privacy with Payment-Channel Networks. Malavolta G, Moreno-Sanchez P, Kate A, Maffei M, Ravi S. CCS '17.
• eltoo: A Simple Layer2 Protocol for Bitcoin. Decker C, Russell R, Osuntokun O. '18.
• SoK: A Taxonomy for Layer-2 Scalability Related Protocols for Cryptocurrencies. Jourenko M, Kurazumi K, Larangeira M, Tanaka K. '19.
• SoK: Off The Chain Transactions. Gudgeon L, Moreno-Sanchez P, Roos S, McCorry P, Gervais A. '19.
• Nitro Protocol. Close T. '19.
• 🎓 Two-Party State Channels with Assertions. Buckland C, McCorry P. FC '19.
• Anonymous Multi-Hop Locks for Blockchain Scalability and Interoperability. Malavolta G, Moreno-Sanchez P, Schneidewind C, Kate A, Maffei M. NDSS '19.

Fungibility

• 🎓 Towards Risk Scoring of Bitcoin Transactions. Möser M, Böhme R, Breuker D. FC '14.

Network

• 🎓 The Bitcoin P2P network. Donet Donet JA, Perez-Sola C, Herrera-Joancomart J. FC '14.
• 🎓 Empirical Analysis of Denial-of-Service Attacks in the Bitcoin Ecosystem. Vasek M, Thornton M, Moore T. FC '14.
• 🎓 Eclipse Attacks on Bitcoin's Peer-to-Peer Network. Heilman E, Kendler A, Zohar A, Goldberg S. USENIX '15.
• 🎓 Hijacking Bitcoin: Routing Attacks on Cryptocurrencies. Apostolaki M, Zohar A, Vanbever L. S&P '17.
• 🎓 Stressing Out: Bitcoin “Stress Testing”. Baqer K, Yuxing Huang D, McCoy D, Weaver N. FC '16.
• 🎓 The Honey Badger of BFT Protocols. Miller A, Xia Y, Croman K, Shi E, Song D. CCS '16.
• Information Propagation in the Bitcoin Network. Decker C., Wattenhofer R. IEEE P2P '13.

Smart Contracts

• "Ethereum": A next-generation smart contract and decentralized application platform. Vitalik Buterin. '14.
• Ethereum: A secure decentralised generalised transaction ledger. Wood G. '14.
• 🎓 Fair Two-Party Computations via Bitcoin Deposits. Andrychowicz M, Dziembowski S, Malinowski D, Mazurek Ł. FC '14.
• 🎓 Step by Step Towards Creating a Safe Smart Contract: Lessons and Insights from a Cryptocurrency Lab. Delmolino K, Arnett M, Kosba A, Miller A, Shi E. FC '16.
• 🎓 EthIKS: Using Ethereum to audit a CONIKS key transparency log. Bonneau J. FC '16.
• 🎓 "Oyente": Making Smart Contracts Smarter. Luu L, Chu DH, Olickel H, Saxena P, Hobor A. CCS '16.
• 🎓 The Ring of Gyges: Investigating the Future of Criminal Smart Contracts. Juels A, Kosba A, Shi E. CCS '16.
• Town crier: An authenticated data feed for smart contracts. Zhang F, Cecchetti E, Croman K, Juels A, Shi E. CCS '16.
• 🎓 A Smart Contract for Boardroom Voting with Maximum Voter Privacy. McCorry P, Shahandashti SF, Hao F. FC '17.
• 🎓 Constant-deposit multiparty lotteries on Bitcoin. Bartoletti M, Zunino R. FC '17.

Formal Methods

• 🎓 Automated Verification of Electrum Wallet. Turuani M, Voegtlin T, Rusinowitch M. FC '16.

Proof of work

• "Proof-of-work": Pricing via processing or combatting junk mail. Dwork C, Naor M. '92.
• Hashcash - A Denial of Service Counter-Measure. Back A. '02.
• 🎓 Cuckoo Cycle: a memory bound graph-theoretic proof-of-work. Tromp J. FC '15.
• 🎓 PieceWork: Generalized Outsourcing Control for Proofs of Work. Daian P, Eyal I, Juels A, Sirer EG. FC '17.
• 🎓 Permacoin: Repurposing bitcoin work for data preservation. Miller A, Juels A, Shi E, Parno B, Katz J. Permacoin. S&P '14.

DAG-based consensus

• SPECTRE: A Fast and Scalable Cryptocurrency Protocol. Sompolinsky Y, Lewenberg Y, Zohar A. '16.
• "PHANTOM": A Scalable BlockDAG protocol. Sompolinsky Y, Zohar A. '18.
• Snowflake to Avalanche: A Novel Metastable Consensus Protocol Family for Cryptocurrencies. Team Rocket. '18.
• Scaling Nakamoto Consensus to Thousands of Transactions per Second. Li C, Li P, Zhou D, Xu W, Long F, Chi-Chih Yao A. '18.
• Blockchain-Free Cryptocurrencies: A Framework for Truly Decentralised Fast Transactions Boyen X, Carr C, Haines T. '16.
• DAGcoin Whitepaper Ribero Y, Raissar D. '15.
• Byteball: A Decentralized System for Storage and Transfer of Value Churyumov A. '16.

Survey, Sociological & Anthropological

• 🎓 Issues in Designing a Bitcoin-Like Community Currency. Vandervort D, Gaucas D, St Jacques R. FC '15.
• 🎓 The Bitcoin Market Potential Index. Hileman G. FC '15.
• 🎓 Cryptographic Currencies from a Tech-Policy Perspective: Policy Issues and Technical Direction. McReynolds E, Lerner A, Scott W, Roesner F, Kohno T. FC '15.
• 🎓 The Other Side of the Coin: User Experiences with Bitcoin Security and Privacy. Krombholz K, Judmayer A, Gusenbauer M, Weippl E. FC '16.
• 🎓 An analysis of Bitcoin OP_RETURN metadata. Bartoletti M, Pompianu L. FC '17.

Applications

• Blockstack Technical Whitepaper. Muneeb A., Ryan S., Jude N, Michael F. '17
• Storj A Peer-to-Peer Cloud Storage Network. Shawn W., Tome B., Josh B., James P., Gordon H., Patrick G., Philip H., Chris P. '18
• IPFS - Content Addressed, Versioned, P2P File System. Benet J. '15
• BigchainDB: A Scalable Blockchain Database. McConaghy T, Marques R, Müller A, De Jonghe D, McConaghy T, McMullen G, Henderson R, Bellemare S, Granzotto A. '17
• 🎓 Commitcoin: Carbon dating commitments with bitcoin. Clark J, Essex A. FC '12.
• OpenTimestamps: Securing Software Updates using the Bitcoin Blockchain Financial Cryptography and Data Security. Todd P, Halpin H. (FC Poster '17)
• 🎓 Decentralized trusted timestamping using the crypto currency bitcoin. Gipp B., Meuschke N., Gernandt A. iConference 2015
• 🎓 Fair and Robust Multi-Party Computation using a Global Transaction Ledger. Kiayias A., Zhouh S., Zikas V. EUROCRYPT '16.

License

This list is released into the public domain.