Ignatev V.A.,  Ponomarev S.A.,  Obukhovskaya E.N. Sbornik zadach i uprazhneniy dlya ustnykh zanyatiy po matematike./Ignatiev V.A.,  Ponomarev S.A.,  Obukhovskaya E.N. A collection of tasks and exercises for oral mathematics classes. In Russian - landofmagazines.com

TransliterationIgnatev V.A., Ponomarev S.A., Obukhovskaya E.N. Sbornik zadach i uprazhneniy dlya ustnykh zanyatiy po matematike.

In EnglishIgnatiev V.A., Ponomarev S.A., Obukhovskaya E.N. A collection of tasks and exercises for oral mathematics classes. In Russian

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