Malema, Mokaba Shirley, et al. “The Efficiency of a Low-Cost Hydrogen Sulphide (H2S) Kit As an Early Warning Test for Assessing Microbial Rainwater Quality and Its Correlation With Standard Indicators Microorganisms”. Nova Biotechnologica Et Chimica, vol. 18, no. 2, Dec. 2019, pp. 133–143, doi:10.2478/nbec-2019-0016.