§ 1. Diophantine equations of arbitrary degree and one unknown § 2. Problems concerning Diophantine equations of two or more unknowns § 3. The equation $x^2 + y^2 = z^2$ § 4. Integral solutions of the equation $x^2 + y^2 = z^2$ for each x-y = ± 1 § 5. Pythagorean triangles of the same area § 6. On squares whose sum and difference are squares § 7. The equation $x^4 + y^4 = z^2$ § 8. On three squares for which the sum of any two is a square § 9. Congruent numbers § 10. The equation $x^2 + y^2 + z^2 = t^2$ § 11. The equation xy = zt § 12. The equation $x^4 - x^2y^2 + y^4 = z^2$ § 13. The equation $x^4+9x^2y^2 + 27y^4 = z^2 § 14. The equation $x^3 + y^3 = 2z^3$ § 15. The equation $x^3 + y^3 = az^3$ with a>2 § 16. Triangular numbers § 17. The equation $x^2 - Dy^2 = 1$ § 18. The equations $x^2 + k = y^3$ where k is an integer § 19. On some exponential equations and others