Sampath Krishnan, S., V. Santhana Krishnan, N. Swarna Sowmya, and R. Kumutha. 2012. “Vibrational Spectra and Ab Initio Studies of L-Prolyl L-Isoleucine”. Asian Journal of Chemistry 24 (6):2533-36. https://asianpubs.org/index.php/ajchem/article/view/9170.