00497naa#a2200169#i#450# EN\\bibl\12161 20250125100357.6 1995-042X 20160921b2016####ek#y0engy0150####ca RUS RU Tourism product differentiation within the domestic tourism Journal article CHERKIZOVO Russian State University of Tourism and Service 2016 9 с. Journal article local Konovalova Elena zh-szf.ru