Sommerhauser, Yorck  1966- <br/><br/>
Hopf algebras and congruence subgroups/ 
Yorck Sommerhauser, Yongchang Zhu. 
 - Providence, R.I.:  American Mathematical Society,  c2012. 
 - v, 134 p.:  ill.;  26 cm. 
 - Memoirs of the American Mathematical Society,  no. 1028  0065-9266; .
 - Memoirs of the American Mathematical Society;  no. 1028. .
<br/><br/> "September 2012 , volume 219, number 1028 (first of 5 numbers)." 
<br/><br/>Includes bibliographical references (p. 125-128) and indexes. 
<br/><br/><label>ISBN: </label>9780821869130 (alk. paper) 0821869132 (alk. paper) 
<br/><br/><label>LCCN: </label>2012015550 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Hopf algebras.<br/>Modular groups.