1. Vitruvius, De Architectura, ca. 35 B.C.
2. Leonardo Da Vinci, Ms. A, f. 48 v; see also, for deviations related to buckling, Ms. A, f, 3 v, ca. 1500.
3. Philosophiae naturalis principia mathematica
4. On the effect of the internal friction of fluids on the motion of pendulums;Stokes;Trans. Cambr. Phil. Soc., IX,1852