(18548) Christoffel = 1997 AN12
Elwin Bruno Christoffel (1829-1900) was a professor at various
German universities. His work on quadratic differential forms,
inspired by Riemann, anticipated some of the results of tensor
theory later developed by Ricci and Levi-Civita.
A complete set of naming citations of the numbered minor planets is available in the Dictionary of Minor Planet Names, edited by Lutz Schmadel.