In the geometry of our ordinary plane, points and lines play different rôles. There exist parallel lines, that is, lines which are not on a common point. In fact, for any given line l, there exists exactly one parallel line on every point which is not on l But there are no parallel points, in the sense of points which are not on a common line. Every two distinct points are on exactly one common line.
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- Ergebn. mathem. Kolloquiums, vol. 8 (1937), 32.Google Scholar
- Cf., in particular, Pauc’s résumé in the pamphlet “Les méthodes directes en Calcul des Variations,” (Paris, Herman, 1941).Google Scholar
- Rend. della Acc. Naz. Linc, vol. 26 (1937).Google Scholar
- Ergebn. math. Kolloquiums, vol. 8 (1937), 25 and Alt, loc. cit.3Google Scholar