Zachariah, D. S. T. J. “Phenolic Profiling of Piper Species by Liquid Chromatography-Mass Spectrometry”. Journal of Spices and Aromatic Crops, vol. 25, no. 2, Dec. 2016, pp. 123-32, https://updatepublishing.com/journal/index.php/josac/article/view/5176.