Clifton, Michael, "Breaking the Glass: A Pattern of Visionary Imagery in W. S. Merwin," in Chicago Review, Vol. 36, No. 1, Summer 1998, pp. 65-82.

Published a year after this poem, Clifton's theory of
poetry does not take "The Horizons of Rooms" into
account, but it does give interesting background to
Merwin's writing style.

Connaroe, Joel, Eight American Poets, University of South Carolina Press, 1997.

This book, a follow-up to Connaroe's successful Six
American Poets
,
presents the works of Merwin and
other poets of his generation who are considered his
equals: Theodore Roethke, Elizabeth Bishop, Robert
Lowell, John Berryman, Sylvia Plath, Allen Ginsberg,
James Merrill, and Anne Sexton.

Hix, H. L., Understanding W. S. Merwin, University of South Carolina Press, 1997.

This book, part of the Understanding Contemporary
American Literature
series, gives an overview of the
changes of Merwin's career, spanning over forty years.

Scigaj, Leonard, Sustainable Poetry: Four American Ecopoets...