Thus, what is explicitly Madhava's work is a source of some debate. The "Yukti-dipika" (also called the "Tantrasangraha-vyakhya"), possibly composed by Sankara Variyar, a student of Jyeṣṭhadeva, presents several versions of the series expansions for sin "θ", cos "θ", and arctan "θ", as well as some products with radius and arclength, most versions of which appear in Yuktibhāṣā. For those that do not, Rajagopal and Rangachari have argued, quoting extensively from the original Sanskrit, that since some of these have been attributed by Nilakantha to Madhava, some of the other forms might also be the work of Madhava.