References: 1. https://doi.org/10.1016/S0022-0248(97)00108-5 (1997)
2. Journal of Solid State Chemistry 165, 35-41, doi:https://doi.org/10.1006/jssc.2001.9486 (2002)
These are important reference papers on this topic, but I fail to grasp exactly how the p-type doping occurs.
Will be grateful to receive help.