^Northern Sorsogon at Ethnologue (18th ed., 2015) (subscription required)
^MacFarland, Curtis D. (1974). The Dialects of the Bikol Area (Ph.D. dissertation). University of New Haven.
^Zorc, David Paul (1977). The Bisayan Dialects of the Philippines: Subgrouping and Reconstruction. Canberra, Australia: Dept. of Linguistics, Research School of Pacific Studies, Australian National University. doi:10.15144/PL-C44. ISBN0858831570.