Superposed point-rows, [47], [48], [49]

Surfaces of the second degree, [166]

System of lines in space, [20], [23]

Systems of conics, [125]

Tangent line, [61], [80], [81], [87], [88], 89, [90], [91], [92]

Tycho Brahe (1546-1601), [162]

Verner, [161]

Vertex of conic, [157], [159]

Von Staudt (1798-1867), [179], [185]

Wallis (1616-1703), [162]