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At the same time Dewar observed series in alkali spectra , Hartley found constant wave-number differences , Balmer discovered a relation connecting wavelengths in the visible hydrogen spectrum , and finally Rydberg derived a formula for wave-numbers of spectral series .
 person: Dewar; person: Hartley; person: Balmer; person: Rydberg
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
 Entities: Dewar, Hartley, Balmer, Rydberg 
Answer:
 person: Dewar; person: Hartley; person: Balmer; person: Rydberg