\mathbb {R} } ⁠. The adjective real, used in the 17th century by René Descartes, distinguishes real numbers from imaginary numbers such as the square...

written Z {\displaystyle \mathbb {Z} } . Here the letter Z comes from German Zahl 'number'. The set of integers forms a ring with the operations addition and...

Hans Klüver (1963) Ye Faerie Chesseman by D. L. Miller (1965) Schach und Zahl by Bonsdorff, Fabel, and Riihimaa (1966) Maximum Tables by The Fairy Chess...

einer notwendigen Bedingung für die Existenz einer ungeraden vollkommenen Zahl". S.-B. Bayer. Akad. Wiss. 1937: 69–72. Nankar, M.L.: "History of perfect...

1997.11990661. JSTOR 2974737. MR 1447977. Lindemann, F. (1882). "Über die Zahl π" [On the number π]. Mathematische Annalen (in German). 20 (2): 213–225...

level. There, under Stumpf's supervision, he wrote Über den Begriff der Zahl (On the Concept of Number) in 1887, which would serve later as the basis...