Call Centre Forecasting

I am a final year student at Leeds Metropolitan University and for my final year project I am looking at the forecasting of calls in the call centre environment. I work in a call centre (part-time) and the company I work for uses Erlang-C to calculate a forecast, however I am struggling to find any other theories and their formulas which I require as part of my research. If you could advise of any methods other Erlang-C then I would be very
grateful.

Thanks,

Stephen Robinson
stephen@robinson123.fsnet.co.uk