Crook, Welton J. <br/><br/>
Abacus arithmetic :  How to perform some calculations on the Chinese abacus / 
Welton J. Crook. 
 - Palo Alto, Calif. :  Pacific Books,  1958. 
 - 69 p. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Arithmetic