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In 1817 his friend , zoologist Heinrich Kuhl ( 1797 – 1821 ) procured an assignment for him at the University of Leiden as a reader of botany , and shortly afterwards , with the help of botanist Sebald Justinus Brugmans ( 1763 – 1819 ) , he held a position at the botanical gardens in Leiden .
 Heinrich Kuhl, University of Leiden, Sebald Justinus Brugmans, Leiden
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
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Answer:
 Heinrich Kuhl, University of Leiden, Sebald Justinus Brugmans, Leiden