Никитинский, В. А., С. В. Пивоварова, and С. В. Шабрацкий. “Not Observable Complex Numbers in the Electrical Engineer and the Physicist”. Eastern-European Journal of Enterprise Technologies, vol. 2, no. 5(50), Jan. 2012, pp. 46-48, doi:10.15587/1729-4061.2011.1790.