Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI)
BERNARDI Enrico and BOVE Antonio,Geometric transition for a class of hyperbolic operators with double characteristics,Japanese journal of mathematics. New series,02892316,The Mathematical Society of Japan,1997,23,1,1-87,https://cir.nii.ac.jp/crid/1390282680233980032,https://doi.org/10.4099/math1924.23.1