The haloed line effect for hidden line elimination
Arthur Appel, F. James Rohlf, Arthur J. Stein.
Siggraph 79, pp. 151--157,
1979. [BibTeX]
The notion of quantitative invisibility and the machine rendering solids
Arthur Appel.
Proceedings of the 22nd ACM National Conference, pp. 387--393, Washington, D.C., United States, ACM Press,
1967. [BibTeX]