Is D.H. Lawrence Poem in the Public Domain?

Dear Rich: We are publishing a book in conjunction with a museum exhibit. The artwork in the exhibit was inspired by D.H. Lawrence's poem, "Whales Weep Not!" On the website, Poets.org, they indicated the poem may still be under copyright by the poet's estate (Copyright © 1964, 1971 by Angela Ravagli and C. M. Weekly, Executors of the Estate of Frieda Lawrence Ravagli. Used by permission of Viking Penguin, a division of Penguin Books USA Inc.) Is the poem in the public domain or do we need permission? 
If the copyright for "Whales Weep Not!" was renewed, it is still under copyright and will not fall into the public domain for several years. The poem was published posthumously in 1932 in the collection, "Last Poems" (Lawrence died in 1930). Copyright law protects such works for 95 years from first publication, provided that it was timely renewed. However, we couldn't find evidence of renewal of "Last Poems" at the Stanford Renewal database. That's not conclusive ("Absence of evidence isn't evidence of absence") and may be due to an error in data conversion or imprecise searching. (The estate had been diligent in renewing Lawrence's other works, including his poetry.) The only definitive proof would be to pay for a certified Copyright Office search.