The Facts on File Companion to British Poetry, 1900 to the Present (2009), edited by James Persoon and Robert R. Watson, contains an entry for Geoffrey Hill by James Persoon. It ends by evoking the "praise songs" of "more contemporary witness" found in Speech! Speech! Persoon cites as example the poems "about the Biafran War and the martyred Biafran poet Christopher Okigbo."
James Persoon is the author of Modern British Poetry (Twayne, 1999) and Hardy's Early Poetry: Romanticism through a "Dark Bilberry Eye" (Lexington, 2000).