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William R. Halliday

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Depths of the Earth: Caves and Caverns of the United States
American caves and caving: techniques, pleasures, and safeguards of modern cave exploration
American Caves and Caving
Depths of the Earth
Proceedings, 1982 3rd International Symposium on Vulcanospeleology
Hawaiian Volcanoes
American Caves and Caving Techniques, Pleasures, and Safeguards of Modern Cave Exploration
American Caves and Caving: Techniques, Pleasures, and Safeguards of Modern Cave Exploration