An interesting history of an incident which unfolded on Yaddo involving Robert Lowell, Flannery O'Connor, and the CIA.
You can buy “Day by Day” here.
NBCC winning poet Mark Rudman has written an introduction to Lowell's work, which includes a chapter on “Day by Day,” which you can find here.
You can also buy John Thompson's piece, which ran in The New York Review, October 1977, a month after Lowell's death, here. A pull quote from this piece appears on the back of “Day by Day.”
Tom Paulin reviews “The Collected Poem” of Robert Lowell in The Observer. “Lowell dominated my generation,” he writes: “his mighty, Marlovian lines had an insistent greatness right from the start.”