"There is a structure theory for bull-free graphs
modulo the structure of triangle-free graphs
and their complements, which again is not easy.
(The bull has a triangular face, with horns or
pendant edges at two of its three vertices.)"
— Peter J. Cameron today
For example —
The bull graph in a book by Clarence R. Wylie, Jr.
(author of the poem "Paradox" (1948)). See no. 6 below —
See also Wikipedia.
Related material —
J. Paul Getty and Minotaur, according to Hollywood —