Explanatory Note 



The series embodies results of Investigations, usually of 

 restricted scope, intended to aid or direct managonent or 

 utilisation practices and as guides for administrative or 

 legislative action. It is issued in limited quantities for the 

 official use of Federal, State or cooperating agencies and in 

 prooessed fonn for economy and to avoid delay in publications. 



Washington, D. Ci 

 May 1960 



