Ritter, C., and J. Gilliard. “ImpuR: A Collection of Diagnostic Tools Developed in R in the Context of Peak Impurity Detection in HPLC-DAD But Potentially Useful With Other Types of Time-Intensity Matrices”. Journal of Statistical Software, vol. 18, no. 9, Jan. 2007, pp. 1-18, doi:10.18637/jss.v018.i09.