 Later generations composed commentaries on the canonical Abhidharma and introduced a variety of exegetical manuals that expound the essentials of the canonical systems. These post-canonical texts are the products of single authors and display fully developed polemical stances and sectarian worldviews of their respective schools. Much of the Theravāda Abhidhamma system is contained in Buddhaghosa’s comprehensive Visuddhimagga (The Path of Purification, fifth century CE). More direct introductory Abhidhamma manuals are Buddhadatta’s Abhidhammāvatāra (Introduction to Abhidhamma, fifth century CE) and Anuruddha’s Abhidhammatthasaṅgaha (Compendium of the Topics of Abhidhamma, twelfth century CE). The Sarvāstivāda tradition preserves in Chinese translation three different recensions of an authoritative Abhidharma commentary or vibhāṣā dated to the first or second century CE, the last and best known of which is called the Mahāvibhāṣā. The vibhāṣā compendia document several centuries of scholarly activity representing multiple Sarvāstivāda branches, most notably the Sarvāstivādins of Kashmir who are known as Sarvāstivāda-Vaibhāṣika. The Sarvāstivāda manual most influential for later Chinese and Tibetan Buddhism, however, is Vasubandhu’s Abhidharmakośa (Treasury of Abhidharma, fifth century CE). The Abhidharmakośa’s auto-commentary contains substantial criticism of orthodox Sarvāstivāda positions, which later Sarvāstivāda-Vaibhāṣika masters attempted to refute. Particularly famous in this category is the Nyāyānusāra (Conformance to Correct Principle) of Saṅghabhadra, a contemporary of Vasubandhu. This comprehensive treatise reestablishes orthodox Sarvāstivāda views and is considered one of the final Sarvāstivāda works to have  survived.[3]