Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) G. Hudson and M. Greenfield,The Speed of Propagation of Brittle Cracks in Steel,Journal of Applied Physics,0021-8979,AIP Publishing,1947-04-01,18,4,405-407,https://cir.nii.ac.jp/crid/1361137045839955712,https://doi.org/10.1063/1.1697664