Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI)
J. Schaer,The Densest Packing of 9 Circles in a Square,Canadian Mathematical Bulletin,0008-4395,Canadian Mathematical Society,1965-04,8,3,273-277,https://cir.nii.ac.jp/crid/1364233270655373056,https://doi.org/10.4153/cmb-1965-018-9