Mazarura , Upenyu. 2013. “Exploring the Influence of Coal Rubble and Pine Bark Substrate Mixes on Germination, Spiral Rooting, Substrate Chemical and Physical Properties: Using Tobacco As Test Crop”. Asian Journal of Agriculture and Rural Development 3 (3):115-26. https://archive.aessweb.com/index.php/5005/article/view/669.