'Co-Descriptive Strings', is the title of a short piece put together in collaboration with my friend Victor Eijkhout ('ayk howt'), then studying mathematics at Nijmegen university. In 1982 McKay and Waterman had come up with the idea of a 'self-descriptive string'. Recognizing that a self-descriptor can be seen as that case of a closed cycle of descriptors whose length is 1, we merely extended their idea to take in cycles of longer length. Since then, there has been an explosion in the literature on the topic. I'm not sure whether or not we were the first to consider longer loops, but to the best of my knowledge, our identification of the 23 'Fibonacci loops' is unique to our paper. A poor quality reproduction can be found here.