Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) MISAWA Seisuke and SAKURAI Takashi and TAKAHASHI Akinori,Estimate of Rock Strength in Non-core Boring Operation,Journal of the Japan Society of Engineering Geology,0286-7737,Japan Society of Engineering Geology,1978,19,2,60-70,https://cir.nii.ac.jp/crid/1390282679072361344,https://doi.org/10.5110/jjseg.19.60