90 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
5. Letters are not permitted in exchange packages. 
6. If donors desire acknowledgments, packages may contain receipt-forms 
to be signed and returned by the establishment or individual addressed. 
Should publications be desired in exchange, a request to that effect may be 
printed on the receipt-form or on the package. 
7. The work carried on by the International Exchange Service is not in 
any sense of a commercial nature, but is restricted to the transmission of 
publications sent as exchanges or donations. Books sold or ordered through 
the trade are, therefore, necessarily excluded. 
8. Specimens are not accepted for distribution, except when permission 
has been obtained from the Institution. 
Respectfully submitted. 
C. G. Assor, 
Assistant Secretary, in charge of Library and Hechanges. 
Dr. Cuartes D. Watcort, 
Secretary, Smithsonian Institution. 
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