21. International commerce; [Clarence M. Zens, managing editor]. Bookmark SuDoc number: C 42.8: (v.nos.&nos.)
22. International commerce; [Clarence M. Zens, managing editor]. Bookmark SuDoc number: C 42.8: (v.nos.&nos.)
23. International commerce; [Clarence M. Zens, managing editor]. Bookmark SuDoc number: C 42.8: (v.nos.&nos.)
24. International commerce; [Clarence M. Zens, managing editor]. Bookmark SuDoc number: C 42.8: (v.nos.&nos.)
25. International commerce; [Clarence M. Zens, managing editor]. Bookmark SuDoc number: C 42.8: (v.nos.&nos.)