All books subject to prior sale. Payment with order; institutions may be billed. Postage additional: $11.00 for the first book, $6.00 each thereafter. Overseas postage billed at approximate cost. Pennsylvania residents must add 6% sales tax. Mastercard, Visa, and American Express accepted, but if you are a bookseller getting a discount, you must pay by check. We are also open to reasonable payment terms. A book may be returned within 7 days of receipt for any reason provided it is in the same condition as sent and prior notice is given. Please insure returns for their full value.