Some Vaishnava literature reverentially link Shiva to characters in its mythologies. For example, in the Hanuman Chalisa, Hanuman is identified as the eleventh avatar of Shiva. The Bhagavata Purana and the Vishnu Purana claim sage Durvasa to be a portion of Shiva. Some medieval era writers have called the Advaita Vedanta philosopher Adi Shankara an incarnation of Shiva.