8 1 50 Kenneth J. Travers Additional Author Le Roy C. Dalton Additional Author mixed material Macmillan Pub 1990 Gary L. Peterson Additional Author mixed material Wadsworth Pub 1985 Richard N. Aufmann Additional Author Vernon C. Barker Additional Author mixed material Boston 1990 Jose Barnos-Netto Additional Author mixed material West Publishing 1985 Paul K. Rees Additional Author Fred W. Sparks Additional Author mixed material McGraw Hill 1991 Robert G. Steni Additional Author mixed material Nelson Hall 1986 Frankin Demana Additional Author Bert K. Waits Additional Author mixed material Addision Wesley 1990 a complete and concrete approach Harold S. Engelshon Additional Author mixed material McGraw Hill 1981