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Fouché, Leo. V: Foundation of the Cape Colony, 1652–1708. Walker, Eric Anderson (编). The Cambridge History of the British Empire. VIII: South Africa, Rhodesia and the Protectorates. Cambridge: CUP Archive. 1936: 1361963 [2016-11-16]. (原始内容存档于2021-03-12). [...] van der Stel recognised the roving tendency among the colonists and tried to arrest it. A proclamation of 1692 illustrated his fears: it stated that colonists were making a living by grazing cattle and bartering in the interior [...]. This seems clear proof that the trekboer, as a distinct type, was coming into existence during the time of van der Stel. [...] Generation after generation of these hardy and self-reliant nomads pushed the frontiers of civilisation further into the wilderness.