6William N. Eskridge,Jr Philip P. Frickey Elizabeth Garrett "Cases and Materials on Legislation Statutes and The Creation of Public Policy "Third Edition ,West Group,2001 P.65
7William N. Eskridge, Jr Philip P. Frickey Elizabeth Garrett "Cases and Materials on Legislation Statutes and The Creation of Public Policy "Third Edition , West Group,2001 P.67
8William N. Eskridge, Jr Philip P. Frickey Elizabeth Garrett "Cases and Materials on Legislation Statutes and The Creation of Public Policy "Third Edition , West Group,2001 P.66