Your best bet for a fact sheet would be to contact Wendy at Swan Support in Datchet, England. She may have one that she can send to you.

As far as determining gender based upon the size of the knob, usually the male swan has the larger knob. However, we have seen cases in which some female swans have a large knob and some male swans have small knobs. So, knob size may be an individual attribute in some swans and such, cannot be used as a viable identifier for gender. The Regal Swan