Characterization of X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis subsp. lactis Richard J. Lloyd, Graham G. Pritchard p. 49–55 https://doi.org/10.1099/00221287-137-1-49
Classification and identification of bacteria by Fourier-transform infrared spectroscopy Helm, D., Labischinski, H., Schallehn, Gisela, Naumann, D. p. 69 https://doi.org/10.1099/00221287-137-1-69