11. QUADRATIC FORMS WITH ANY ALGEBRAIC NUMERICAL COEFFICIENTS.
Our present knowledge of the theory of quadratic number fields[25] puts us in a position to attack successfully the theory of quadratic forms with any number of variables and with any algebraic numerical coefficients. This leads in particular to the interesting problem: to solve a given quadratic equation with algebraic numerical coefficients in any number of variables by integral or fractional numbers belonging to the algebraic realm of rationality determined by the coefficients.
The following important problem may form a transition to algebra and the theory of functions:
[25] Hilbert, "Ueber den Dirichlet'schen biquadratischen Zahlenkörper," Math. Annalen, vol. 45; "Ueber die Theorie der relativquadratischen Zahlenkörper," Jahresber. d. Deutschen Mathematiker-Vereinigung, 1897, and Math. Annalen, vol. 51; "Ueber die Theorie der relativ-Abelschen Körper," Nachrichten d. K. Ges. d. Wiss. zu Göttingen, 1898; Grundlagen der Geometrie, Leipzig, 1899, Chap. VIII, § 83 [Translation by Townsend, Chicago, 1902]. Cf. also the dissertation of G. Rückle, Göttingen, 1901.