Impact analysis for program evaluation / Mohr, Lawrence B. Policy sciences. Evaluation research (Social action programs) 361 SAG 1992 A016 Or. Originally published: Chicago, Ill. : Dorsey Press, c1988. Newbury Park : Sage Publications, c1992. c1992. Text xviii, 217, ix p. : http://www.loc.gov/catdir/enhancements/fy0655/92026388-t.html http://www.loc.gov/catdir/enhancements/fy0660/92026388-d.html