1. Methods of measurement and definition of surfaces;Becker;Microtecnic,1950
2. Analysis of real contact area of a paper-based wet friction material;Otani;J Jpn Soc Tribologists,1994
3. Contact characteristics of paper-based friction material (Pt.1);Otani;J Jpn Soc Tribologists,1999
4. On the measuring method for contacting area;Sakurai;J Mech Eng Laboratory,1952
5. Estimation of real contact area of paper-based friction materials for wet clutches by interference method using scanning microscope;Eguchi;J Jpn Soc Tribologists,1997