ボルツァーノ＝ワイエルシュトラスの定理
↑ Bartle & Sherbert 2000, p. 78 (for R)
↑ Fitzpatrick 2006, p. 52 (for R), p. 300 (for R).
↑ Fitzpatrick 2006, p. xiv.
↑ Bartle & Sherbert 2000, pp. 78–79.