# Combinatory Logic * [Flattening Combinators: Surviving Without Parentheses] by Chris Okasaki (2003) ([DOI]) * [Combinatorial Analysis and Computers] by Marshall Hall Jr. and Donald E. Knuth (1965) [Flattening Combinators: Surviving Without Parentheses]: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/3E99993FE5464986AD94D292FF5EA275/S0956796802004483a.pdf/theoretical-pearls-flattening-combinators-surviving-without-parentheses.pdf [DOI]: https://doi.org/10.1017/S0956796802004483 [Combinatorial Analysis and Computers]: https://web.archive.org/web/20170904072400/http://poncelet.math.nthu.edu.tw/disk5/js/computer/hall-knuth.pdf