For citations:

Gavrilov A.A. EARTH RELIEF – WAYS OF KNOWING (TOWARDS THE 30 ANNIVERSARY OF M.V. PIOTROVSKIY BOOK PUBLICATION “TOWARDS KNOWLEDGE OF THE EARTH PRINCIPLES”). Geomorfologiya. 2015;(1):113-116. (In Russ.) https://doi.org/10.15356/0435-4281-2015-1-113-116