Khadeer Pasha, S.K., et al. “Synthesis, Characterization and Effect of Sintering Temperature on the Humidity Sensing Properties of Nanocrystalline PbO”. Asian Journal of Chemistry, vol. 23, no. 7, Mar. 2011, pp. 3109-13, https://asianpubs.org/index.php/ajchem/article/view/10615.