21430
Innovations and contributions to climbing Harding 's most important contribution to climbing technique was to perfect and popularise the hand jam ; a method of climbing cracks using the fleshy part of the thumb in conjunction with the back of the hand to grip the inner part of the crack .
 Harding
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Harding