67260
The company also worked on single-seat fighter designs , which culminated in the He 49 and later with the improved He 51 .
 He 49, He 51
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 He 49, He 51