1. Ahmed Hashem and Erich Kleinpeter, et al., The Chemistry of 2(5H)-Furanones, Advances in Heterocyclic Chemistry, Academic Press, Volume 81, 2001, Pages 107-165.2. Sunil V. Pansare and Eldho K. Paul, Organocatalytic asymmetric direct vinylogous aldol reactions of γ-crotonolactone with aromatic aldehydes. RSC, Issue 3, 2011.