Sarva-tathāgata-tattva-saṃgraha 

An extensive work in five parts. Composed during the late decades of the 7th century ce, it forms the root text of yoga-tantra. Though it had some popularity in early Tibetan Buddhism, it was more important in Sino-Japanese forms of tantric Buddhism where attention was focused upon its first section, the Mahā-maṇḍala, which circulated separately under the title of the Vajra-śekhara Sūtra.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)