The point characteristic as a series solution of the equations satisfied by it
H. A. Buchdahl · Journal of the Optical Society of America A · 1989
Except in rare cases, characterized by the presence of special symmetries, it is not possible to find an expression in closed form for the point characteristic V, and one must be content with approximations of one kind or another. Here the representation of V as the product of the (geometrical) distance between the terminal points and a Taylor series in appropriately chosen variables is examined in the absence of any symmetries.