Assiddiqi, Z., S. van Balen, and N. J. Collar. “Mystery Flycatchers in Sumatra - Rück’s Blue-Flycatcher or White-Tailed Flycatcher?”. KUKILA, Vol. 23, no. 1, Dec. 2020, pp. 19-26, http://kukila.org/index.php/KKL/article/view/613.