Answer the following question: Question: "What writings were unavailable for research to Madhavacharya?"  Context: "Later Indian materialist Jayaraashi Bhatta (6th century) in his work Tattvopaplavasimha ("The upsetting of all principles") refuted the Nyaya Sutra epistemology. The materialistic Cārvāka philosophy appears to have died out some time after 1400. When Madhavacharya compiled Sarva-darśana-samgraha (a digest of all philosophies) in the 14th century, he had no Cārvāka/Lokāyata text to quote from, or even refer to."  Answer:
Answer:
Cārvāka/Lokāyata text