V. P. S. Verma and S. P. Pant, “Performance of Slash Pine (<I>Pinus elliottii</I> Engelm.) Vis-a-vis Chirpine (<I>Pinus roxburghii</I> Sargent) in Respect of Oleoresin Yield at Dehra Dun”, Indian Forester, vol. 104, no. 11, pp. 768–771, Nov. 1978.