1 Flowerbase Glasshouse Business Networks BV (http://www2.flowerweb.nl/flowerbase/)
2 http://www.all-creatures.org/
3 http://www.columnar-cacti.org/cereus/index.html
4 http://www.smith.edu/garden/
5 http://www.desertusa.com/mag99/july/papr/nbcereus.html
6 http://cactiguide.com/graphics/c_peruvianus_e_600.jpg
7 http://www.theamateursdigest.com/30185.jpg
8 http://www.fortunecity.com/greenfield/swallowtail/785/cereus_albicaulis_flower.jpg