Kyabjé Chhimed Rigdzin Rinpoche was the Head of the Department of Indo-Tibetan Studies at Visva Bharati University. (That is one of the best-known and best-regarded universities in India.) He was Ngakpa Chögyam’s doctoral (PhD) dissertation adviser, as well as his Lama. (“Ngakpa Chögyam” is another name for Ngak’chang Rinpoche.)
This letter formally recommends Ngakpa Chögyam for a doctoral degree (PhD). (The degree was in fact given in 1989.) Rinpoche signed himself “CR Lama” on this and most other documents.
You can click on the letter, or here, to see a larger, clearer version.