Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) Nakao Ken-ichi and Okawa Hirotada and Maeda Kei-ichi,On the energy extraction by nonlinear collisional Penrose process,Meeting Abstracts of the Physical Society of Japan,2189-0803,The Physical Society of Japan,2017,72.2,0,339-339,https://cir.nii.ac.jp/crid/1390845713023487104,https://doi.org/10.11316/jpsgaiyo.72.2.0_339