Waveguide Bends & Tapers

Can anyone please tell me a good source for design formulae for Rectangular Waveguide bends and tapers,

Thanks,
-Prakash

Really? No one can help?

I think that in any microwave book you can find some suggestion... Mattei is an example.
you can try to simulate them with a 3D em simulator like HFSS or mician.

Bye