Tibetan Buddhism has a unique and special class of texts called "terma" (Tibetan: "gTer-ma"). These are texts (or ritual objects, etc.) believed either composed or hidden by tantric masters and/or elementally secreted or encoded in the elements and retrieved, accessed or rediscovered by other tantric masters when appropriate. Termas are discovered by tertöns (Tibetan: "gTer-stons"), whose special function is to reveal these texts. Some termas are hidden in caves or similar places, but a few are said to be 'mind termas,' which are 'discovered' in the mind of the tertön. The Nyingma school (and Bön tradition) has a large terma literature. Many of the terma texts are said to have been written by Padmasambhava, who is particularly important to the Nyingmas. Probably the best known terma text is the so-called "Tibetan book of the dead", the "Bardo Thodol".