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Sturmey AW, etc.[1]
  Number of gear teeth        
Gear Sun Gear 1 Pinion to Sun 1 Pinion to Ring 1 Ring gear 1 Path, 1=R to P, 2=Direct, 3=P to R Gear Drive Ratio Drive ratio as fraction Ratio incre- ment
1 20 20 20 60 1 0.750    3/4   
2 20 20 20 60 2 1.000 1        1.333
3 20 20 20 60 3 1.333 1   1/3  1.333

[1]
John Allen:
Tooth counts verified:
http://www.users.globalnet.co.uk/~hadland/1theory.pdf
http://www.users.globalnet.co.uk/~hadland/2tables.pdf