1. Mathematical Classification Techniques for Non-Static Document Collections, with Particular Reference to the Problem of Relevance, in Classification Research, Proceedings of the 2nd International Study Conference, Elsinore, Denmark, 1964, pp. 177–219.
2. The use of second order descriptors for document retrieval
3. in Discussion of Hillman, D. J., loc. cit.
4. An Investigation of the Laws of Thought on Which Are Founded the Mathematical Theories of Logic and Probabilities, 1854, Dover Publications, Inc., New York.