Thompson, N.P. and Heimsch, C. 1964. Stem anatomy and aspects of development in tomato. American Journal of Botany 51: 7-19. [1]
Ewers, F.W. 1982. Secondary growth in needle leaves of Pinus longaeva (bristlecone pine) and other conifers: Quantitative data. American Journal of Botany 69: 1552-1559. [2]