Principles of Penetrants (first edition; Chicago: Magnaflux Corp., c1963), by Carl E. Betz (page images at HathiTrust)
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Principles of Penetrants (first edition; Chicago: Magnaflux Corp., c1963), by Carl E. Betz (page images at HathiTrust)
New Online Books
http://catalog.hathitrust.org/Record/005792712