Hayes, Samuel Perkins <br/><br/>
Measuring the results of development projects :  a manual for the use of field workers / 
Samuel Perkins Hayes. 
 - Paris :  UNESCO,  1961. 
 - 100 p. 
 - Monographs in the applied social sciences .
<br/><br/><label>No. de Clasificación Universal Decimal: </label>338.984 =20 "1961" HAY.