. . "Ryūgaku Ishizuka"@en . "石塚龍學" . "1945" . . "龍學 石塚" . "I. Ryugaku" . "石塚龍學" . "石塚龍學" . "Ryūgaku" . "Ryūgaku"@en . "Ryugaku" . . "Ryugaku Ishizuka" . . "Ishizuka" . "石塚" . "Ishizuka, Ryūgaku" . "Ryugaku Ishizuka" . . "龍學" . "Ishizuka"@en . . "1881" . . . "Ishizuka"@nl-NL . "I." . "Ryugaku" . .