K. M. Ivanov, T. K. Varbov, and G. T. Velev, “CALCULATION OF LOSSES OF ACTIVE POWER AND ENERGY IN TRANSMISSION LINES AND TRANSFORMERS, AS A PART OF THE ELECTRICAL DISTRIBUTION POWER NETWORK”, ETR, vol. 3, pp. 107–110, Jun. 2017, doi: 10.17770/etr2017vol3.2657.