Tyuflin Yu.S. Opredeleniye kovariatsionnoy matritsy prostranstvennykh koordinat tochek geometricheskoy modeli. — «Geodeziya. kartografiya i aerofotosyemka». 1972. vyp. 15. https://science.lpnu.ua/sites/default/files/journal-paper/2018/apr/11605/tyuflin.pdf