The ‘Thirty Verses’, a key Yogācāra work by Vasubandhu which can be viewed as a companion to his Viṃśatikā. The work briefly discusses the manner in which the duality of experience arises, the nature of mind and its operations, the three natures (tri-svabhāva), and the process by which delusive duality (vikalpa) may be eliminated through an understanding that all experience is no more than an illusory construct of cognition (vijñapti-mātra). Interpretation of the text is controversial since it may be understood in an ontological sense that denies external reality, thus implying idealism, or else in an epistemological sense which explains the manner in which cognitive experience is fabricated by the mind. The text survives in Sanskrit as well as a Tibetan and two Chinese translations. The Chinese translation by Hsüan-tsang formed the basis for his commentorial compilation, the Cheng-wei-shi-lun (Skt., Vijñapti-mātratā Siddhi).