Columbia subject headings:
Earthworks (Art)--Netherlands.
Natural landscaping--Netherlands.
Roy, Louis G. le (Louis Guillaume), 1924---Criticism and interpretation.
Trash art--Netherlands.
Harvard subject headings:
Earthworks (Art)--Netherlands.
Ecocathedral (Mildam, Netherlands)
Landscape architecture--Netherlands--Mildam.
Roy, Louis G. le (Louis Guillaume), 1924-
Princeton subject headings:
Landscape architecture.
Roy, Louis G. le (Louis Guillaume), 1924-