There's a book by Robert M Nelson called "Place and Vision: The
function of Landscape in Native American Fiction", American Indian
Studies Vol 1, Peter Lang Publishing, 1993.It looks at Silko, Momaday
and Welch and is quite interesting.
Other articles:-
Schweninger, L, "Writing Nature: Silko & Native Americans as Nature
Writers", MELUS Vol 18, pp47-60, summer 1993.
Allen, Paula Gunn, "Special Problems in teaching LMS' 'Ceremony'",
American Indian Quarterley, vol 14, p379-86, Fall 1990.
Garcia, R "Senses of Place in Ceremony", MELUS Vol 10, p37-48, winter
1993.
American Indian 1/4ly,Vol 12, p229-49, Laguna Symbolic Geography and
Silko's Ceremony"
Hope this helps!