M. Umashankara, M. Nanda, M. Sonar, and K. N. Ganesh, “4(R/S)-Amino/Guanidino-substituted Proline Peptides: Design, Synthesis and DNA Transfection Properties”, Chimia, vol. 66, no. 12, p. 936, Dec. 2012, doi: 10.2533/chimia.2012.936.