39793
For example , in particle physics a system is in use where every quantity is expressed by only one unit of energy , the electronvolt , with lengths , times , and so on all converted into electronvolts by inserting factors of speed of light " c " and the reduced Planck constant " ħ " .
 Planck
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Planck