Boyle, R., Metaphor in Hopkins (Chapel Hill, 1960)
Gardner, W.H., Gerard Manley Hopkins - A Study of Poetic Idiosyncrasy in Relation to Poetic Tradition - (Oxford University Press, 1958)
Leavis, F.R., New Bearings in English Poetry (Chatto and Windus, 1932)
Mariana, P., Commentary on the Complete Poems of Gerard Manley Hopkins (London, 1970)
Schneider, E., The Dragon in the Gate: Studies in the Poetry of Gerard Manley Hopkins (Berkeley and Los Angeles, 1968)