in 1980 Ron Brown published a booklet called "A simple two-queen system".
This should be available from English bee-book suppliers such as BEE Books
New and Old (UK tel 01823 698781) or Northern Bee Books who will take
payment in non-UK currency and can be contacted at [log in to unmask]
The essential feature is to run two queens so as to get lots of workers
ready for the main flow.
Brian Gant