Henry Wadsworth Longfellow (1888). “Longfellow's Days: The Longfellow Prose Birthday Book : Extracts from the Journals and Letters of H. W. Longfellow”
Subrahmanyan Chandrasekhar, Kameshwar C. Wali (2001). “A Quest for Perspectives: Selected Works of S. Chandrasekhar : with Commentary”, p.1286, World Scientific