2173
Rather than the projective linear transformations which were normally regarded as giving the fundamental Kleinian geometry on projective space , they concerned themselves also with the higher degree birational transformations .
 person: Kleinian
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 person: Kleinian