Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) Masahiko Kobayashi and Kou Yamada,A design method for unknown input observer for non-minimum phase systems,SPIE Proceedings,0277-786X,SPIE,2007-12-10,6794,,67940C,https://cir.nii.ac.jp/crid/1871428068242100096,https://doi.org/10.1117/12.784172