TY JOUR TI CONDITIONS AND PREREQUISITES OF DEVELOPMENT OF CLUSTERS IN THE SPHERE OF YOUTH TOURISM IN THE NORTH-WEST FEDERAL DISTRICT KW youth tourism KW tourism product KW motivation of the consumer of tourism services KW special types of tourism KW state regulation of tourism activities JO Universities for Tourism and Service Association Bulletin AU Grishin , S.. AU Karpova , G.. PY 2016 IS 10 PB Russian State University of Tourism and Service