58823
Not all aromatic compounds are benzene-based ; aromaticity can also manifest in " heteroarenes " , which follow Hückel 's rule ( for monocyclic rings : when the number of its π electrons equals 4 " n " " + " 2 , where " n " " = " 0 , 1 , 2 , 3 , ... ) .
 Hückel
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Hückel