N. B. Singh, D. Kumar, G. S. Rawat, R. K. Gupta, K. Singh, and S. S. Negi, “Clonal Evaluation on Poplar (<I>Populus deltoides Bartr.</I>) in Eastern Uttar Pradesh. II - Estimates of Genetic Parameters in Field Testing”, Indian Forester, vol. 127, no. 2, pp. 163–172, Feb. 2001.