Numerous other commentaries are referenced in other Indian historical texts, but these manuscripts are either lost or yet to be found. Starting around 11th- to 12th century CE, Udayana wrote a primary work, that built upon and expanded the theories on reason found in Nyayasutras. Udayana's work created the foundation for Navya-Nyaya (new Nyaya) school. The Hindu scholar Gangesa of 13th- or 14th-century, integrated the Gautama's Nyayasutras and Udayana's Navya-Nyaya work, to create the influential "Tattvacintāmaṇi" text considered a masterpiece by scholars.