(en) Barbara Liskov, « Abstraction mechanisms in CLU », Communications of the ACM, , p. 564-576 (lire en ligne)
appfolio.com
engineering.appfolio.com
(en-US) Noah Gibbs, « Ruby's Roots and Matz's Leadership », sur AppFolio Engineering (consulté le ) : « Matz feels that blocks are the greatest invention of Ruby (I agree.) He got the idea from a 1970s language called CLU from MIT, which called them “iterators” and only allowed them on certain loop constructs. »
doi.org
(en) Barron, D. W, « The Main Features of CPL », The Computer Journal, , Volume 6, Issue 2, pages 134-143 (lire en ligne)
mit.edu
publications.csail.mit.edu
(en) Barbara Liskov, A history of CLU (lire en ligne)