46383
Then , by generalizing the direction-speed-polarization relation for calcite , he accounted for the directions and polarizations of the refracted rays in doubly-refractive crystals of the " biaxial " class ( those for which Huygens 's secondary wavefronts are not axisymmetric ) .
 person: Huygens
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Huygens 
Answer:
 person: Huygens