នេះ Link មិន​មាន​ក្នុង​ភាសា​របស់​អ្នក, មើល​ក្នុង: English (en),
ឬ​ប្រើ​កម្មវិធី​បកប្រែ Google:  

http://holmgren.com.au/permaculture/

David Holmgren is regularly involved in teaching on a variety of permaculture courses including the well known Permaculture Design Certificate course. He also offers workshops, and talks at a diverse range of events and venues.