[PurplePanda]

I've seen this notation quite commonly.

I haven't looked at the link but based on your quote your comment about page 14 doesn't look right. The different notation doesn't change the number of times you need to write the operator.

Your new equation is just writing the same thing on each side, but using a different notation. It's like a=a. Whereas their equation is apparently giving an identity.

[thomaskcr]

I've never seen it but I am trying to think back to all of those times I worked both directions on a proof and just shrugged in the middle =p.

Ah -- you're totally right on my last sentence. Thank you.