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Books about Poortman:
Leven en werken van J.J. Poortman by Klever W.N.A. (1971)
Wiki information Poortman:
Johannes Jacobus Poortman, studied philosophy and psychology at Groningen University under Professor Gerardus Heymans. In 1919 he received his Master of Arts; many years later he would also earn a Ph.D.. He was also a theosophist. Poortman studied at...
Guzmania poortmanii is a species of plant in the Bromeliaceae family. It is endemic to Ecuador. Its natural habitat is subtropical or tropical moist montane forests. It is threatened by habitat loss.