Rocha-Mendoza, I., D. R. Yankelevich , M. Wang , K. M. Reiser , C. W Frank , A. Knoesen, “Sum Frequency Vibrational Spectroscopy: The Molecular Origins of the Optical Second Order Nonlinearity of Collagen”, Biophys. J., v. 93, n. 12, p. 4433-4444 (2007) https://dx.doi.org/10.1529/biophysj.107.111047