Gusev, G.N., V.V. Yepin, and R.V. Tsvetkov. 2018. “On Some Problems of Measuring Systems Based on Hydrostatic Leveling for Long-Term Measurements”. Perm Federal Research Centre Journal, no. 4 (July): 70-76. https://doi.org/10.7242/1998-2097/2017.4.11.