Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) Motoichi Ohtsu and Motonobu Kourogi and K. Nakagawa,Highly accurate frequency counting system for 1.5-μm wavelength semiconductor lasers,SPIE Proceedings,0277-786X,SPIE,1993-04-30,1837,,205,https://cir.nii.ac.jp/crid/1872272492593278848,https://doi.org/10.1117/12.143676