Basis of the initial course of mathematics Textbook for students specializing in primary education "institutions providing secondary special education (neck) / Osnovy nachalnogo kursa matematiki Uchebnoe posobie dlya uchashchikhsya spetsialnosti "Nachalnoe obrazovanie" uchrezhdeniy, obespechivayushchikh poluchenie srednego spetsialnogo obrazovaniya (GRIF)