Dear Heiner,

A good place to start with is of course Lamotte’s Traité, which alludes several times to hells in general and the Sañjīva hell in particular. See especially Étienne Lamotte, Le traité de la Grande Vertu de Sagesse, vol. 2, Louvain, 1981 (1949), pp. 956-958, and passim. On Buddhist descriptions of hell, the best treatment to date is certainly, again in French, Marc Tiefenauer, Les enfers indiens, histoire multiple d’un lieu commun, Leiden, Brill, 2018, pp. 89-146. Both works contain numerous bibliographical references. The most complete treatment is very likely to be the one occurring in the Saddharmasmṛtyupasthānasūtra, a Sanskrit manuscript of which is currently being edited (see D.M. Stuart, A Less Traveled Path : Saddharmasmṛtyupasthāsūtra, chapter 2, 2 vol. Beijing and Vienna, 2015).

Best,

Vincent