Re: "Spring"

The book should now be in the public domain.

It was self-published in 1961 (was it even ever copyrighted?) That is over 50 years:

Published from 1923 - 63 - When published with notice3 - 28 years + could be renewed for 47 years, now extended by 20 years for a total renewal of 67 years. If not so renewed, now in public domain

3 Under the 1909 Act, works published without notice went into the public domain upon publication. Works published without notice between 1-1-78 and 3-1-89, effective date of the Berne Convention Implementation Act, retained copyright only if efforts to correct the accidental omission of notice was made within five years, such as by placing notice on unsold copies. 17 U.S.C. § 405. (Notes courtesy of Professor Tom Field, Franklin Pierce Law Center and Lolly Gasaway)

http://www.unc.edu/~unclng/public-d.htm