The following websites can provide more information and advice:
DISCLAIMER: This list has been written for educational purposes only, it can not be used for diagnosing or treating a health problem or a disease. If you have or suspect you may have a health problem, you should consult your doctor. No responsibility can be accepted for information on any linked page. Please read the provider's own disclaimer where appropriate. Inclusion in this list in no way implies endorsement for particular organisations or linked material.