On certain Tetrahedra specially related to four Spheres meeting in a Point

Samuel Roberts
1880 Proceedings of the London Mathematical Society  
On certain Tetrahedra, fyc. 117 * Or, if two conies a, )3 intersect in the points a, b, e, d, and through d we draw a transversal meeting a in A, and & in I, and if/> is a fixed point on a and q a fixed point on £, we see at once by anharmonic ratios, taking four positions, that the intersection of the lines kp, Iq moves on a conic through a, b, e, p, q. "
doi:10.1112/plms/s1-12.1.117 fatcat:wotluq2uufabdp5a5qplntege4