@book{zobel_sprague_1998, title={Juvenile wood in forest trees}, ISBN={3540640320}, publisher={Berlin; New York: Springer}, author={Zobel, B. J. and Sprague, J. R.}, year={1998} }
 @article{mckeand_jett_sprague_todhunter_1987, title={Summer wax grafting of loblolly pine}, volume={11}, journal={Southern Journal of Applied Forestry}, author={McKeand, S. E. and Jett, J. B. and Sprague, J. R. and Todhunter, M. N.}, year={1987}, pages={96–99} }