Entertaining geometry in free air and at home / Author: Perelman I. and . - Issued by . : Time, 1925. — 256 s. The book is not written so much for the friends of mathematics as for its enemies. She is referring mainly not to those who already have a penchant for mathematics, and not to those who have not yet begun to study it at all. The author intended the book most of all for that vast category of readers who got acquainted in school (or are now still getting acquainted) with this science without much interest and animate, feeding to it at best only cold reverence. To make geometry attractive to them, to inspire hunting and to cultivate a taste for its study is the direct task of the present book. The best way to do this is to show the subject, to some extent known to the reader, with a new, unfamiliar, sometimes unexpected side that can arouse interest and attract attention.