This definition appears somewhat frequently
See other definitions of PDF
Samples in periodicals archive:
40+ years of grass-roots, ecological eye-opening. Planet Drum Foundation was founded in San Francisco, CA in 1973. In association with community activists and ecologists, Planet Drum developed the concept of a bioregion.
The city of Bahia de Caraquez on Ecuador?s Pacific coast is committed to becoming ecologically sustainable. Planet Drum Foundation.