@article{khan_siddiqui_2007,  title={Size variation in the vascular cambium and its derivatives in two Alstonia species},  volume={21},  ISSN={0102-3306},  url={https://doi.org/10.1590/S0102-33062007000300003},  DOI={10.1590/S0102-33062007000300003},  number={3},  journal={Acta Botanica Brasilica},  publisher={Sociedade Botânica do Brasil},  author={Khan, Moin A. and Siddiqui, Badruzzaman},  year={2007},  month={Jul},  pages={531–538} }