Robert Frost, “The Lesson for Today”, The Poetry of Robert Frost, ed. Edward Connery Lathem, (New York: Holt, Rinehart and Winston, 1969)
David A. Sohn, Richard Tyre, Frost: The Poet and His Poetry, (Holt, Rinehart and Winston, 1967) P.X.
Louis Untermeyer, ed. The Pocket Book of Robert Frost’s Poems, (Washington Square Press, 1962) p. 16