Wu, S., Tinant, B., Declercq, J.-P., & Van Meerssche, M. (1987). Crystal-structure and Conformation of Short Linear Peptides .4. Glycyl-glycyl-l-isoleucine Monohydrate Methanol Solvate. Societes Chimiques Belges. Bulletin, 96(6), 443-448. https://doi.org/10.1002/bscb.19870960605 (Original work published 1987)