000			00361nam a2200133Ia 4500
008			130225s9999 xx 000 0 und d
100			_aHeady, Earl O., Scoville, O.J.
245			_aPrinciples of conservation economics and policy
260			_aIowa _c1951
300			_a364-414 p.
440			_aIowa Agricultural Experiment
901			_a32461
942			_cB _2udc
999			_c6254 _d6254