R. Pischel, Epigraphia Indica 8 (1905-06); V. M. Kulkarni, Kūrmaśatakadvayam: two Prakrit poems on tortoise who supports the earth (Ahmedabad: L.D. Institute of Indology, 2003). Kulkarni's book as available via the literature search engine Jain Quantum, https://jainqq.org/about.