El-Sheekh, Mostafa M, et al. “Induction of Sexual Reproduction and Zygospore Patterns in the Filamentous Green Alga Spirogyra (Conjugatophyceae: Zygnematales)”. Journal of BioScience and Biotechnology, vol. 6, no. 2, Apr. 2018, pp. 147-54, https://editorial.uni-plovdiv.bg/index.php/JBB/article/view/157.