https://www.cpr.cuhk.edu.hk/sc/event/the-north-cave-at-xiangtangshan-buddhas-of-the-three-ages-and-eight-directions-and-the-sixteen-princely-bodhisattvas-by-dr-katherine-renhe-tsiang/
The North Cave at Xiangtangshan: Buddhas of the Three Ages and Eight Directions, and the Sixteen Princely Bodhisattvas by Dr. Katherine Renhe Tsiang