Oguchi C.t et Y. Matsukura, Microstructural influence on strength reduction of porous rhyolite during weathering, Zeitschrift fur Geomorphologie. Supplementband Zeitschrift fur Geomorphologie. Supplement;Zeitschrift fur Geomorphologie. Supplementary issue Annals of geomorphology. Supplement;Annales de geomorphologie. Supplement, 119, 1999, pp. 91-103