Research Tented Circus
Zippo's website has many very useful links to circus websites, publications, organisations, etc. Recommended for researchers.
Cirque Surreal : Phot : Mike Brittain
www.zipposcircus.co.uk/link.html
As part of the history of late twentieth century British Circus, you might want to read Gerry Cottle's recently published
Confessions of a Showman
by Gerry Cottle and Helen Batten (€27, published by Vision)