Tri-svabhāva-nirdeśa 

‘The Treatise on the Three Natures’, a key Yogācāra work in 38 verses by Vasubandhu, thought by some to have been his last work. It covers similar ground to his Triṃśikā but deals with his interpretation of the ‘three natures’ (tri-svabhāva) theory at greater length. The work is important since it clearly demonstrates through the analogy of a magically created elephant that early Yogācāra is not an idealistic system but rather deals with epistemological matters. The text survives in Sanskrit and a Tibetan translation but curiously no Chinese version is known.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)