And in 1942, he wrote a book, (speaking in foreign language) It was translated into English only 14 years later, “Wild Animals in Captivity”. And this is the important start of scientific zoo biology. So this is probably his main achievement. And there, the main thing he proved is that in zoo animals, not the quantity of the space is important, but the quality of the space is the important thing. So if you, for example, give a gibbon 20 hectares, that’s a natural territory ace. But 20 hectares of grassland, he and she will not be happy. But if you give them 50 square meters of trees and plants, as they have in the wild, they are happy. Especially since they do not need the full territory size as in the wild, since the keeper is regularly bringing the food.