Scholars of philophy should never forget the wonderful online resource, originally made on paper by Karl Potter, titled Encyclopedia of Indian Philosophies (1st ed. 1975, revised in 1983 and 1990). I say scholars of philosophy tout court since what has been thought and written in India does not belong to the country, but to the human civilization.
This site is continuosly updated and contains a bibliography of the philosophical literature of India during its classical phase and the secondary material on this literature that is available (for the most part) in English,
namely primary texts and literature about authors, and secondary literature on all the major philosophical schools and systems: Ābhidharma/Theravāda, Advaita Vedānta, Buddhist Logic/Sautrāntika, Grammarian or Vyākaraṇa, General Buddhism, especially Mahāyāna, General Hinduism, Jainism, Kashmir Śaivism, Madhyamaka, Sāṃkhya, Yoga and so on.