@article{Clark:1987, author = "Adrian Clark", title = "Halftone output from {\TeX}", journal = TUB, volume = "8", number = "3", year = "1987", pages = "270--274" } @unpublished{Clark:1989, author = "James Clark", title = "{DVITOPS} User Manual", year = "1989", note = "unpublished machine-readable documentation" } @article{Clark:1991, author = "Adrian Clark", title = "Practical halftoning with {\TeX}", journal = TUB, volume = "12", number = "1", year = "1991", pages = "157--165" }