Liu, Y., Y. Jiao, B. Yin, S. Zhang, F. Qu, and X. Wu. “Hierarchical Semiconductor Oxide Photocatalyst: A Case of the SnO2 Microflower”. Nano-Micro Letters, vol. 5, no. 4, Oct. 2013, pp. 234-41, doi:10.1007/BF03353754.