JOHNSON K GEORGE, P N RAVINDRAN, K NIRMAL BABU, R RAMAKRISHNAN NAIR,. 1992. “Piper Barberi Gamble - a Redescription of the Species With a Note on the Karyotype”. Journal of Spices and Aromatic Crops 1 (1):88-93. https://updatepublishing.com/journal/index.php/josac/article/view/4289.