multilayer air coil

Can anyone tell me a reliable formula for calculating the inductance of a mutilayer air core coil?

You can verify this page, maybe it will help....
hxxp://www.coilws.com/c_winding_main/AirCoil_Inductor.php
hxxp://www.ee.surrey.ac.uk/Workshop/advice/coils/air_coils.html
wxw.classictesla.com/download/multilayer.pdf

Thanks a lot. That pdf is exactly what I'm looking for. The other links don't work though.

all above are really very usefull but i have a small question in all the coil desgin software they asking for the wire diameter so if i have a coil with a plastic isolator which diameter i will use the wire or the wire+insolator