S. Ab Hamid, M. S. Salleh, K. Thevan, and N. A. Hashim, “Distribution and Morphometrical Variations of Stingless Bees (Apidae: Meliponini) In Urban and Forest Areas of Penang Island, Malaysia”, JTRSS, vol. 4, no. 1, pp. 1–5, Dec. 2016.