Animated-Teeth.com: Canker Sores / Aphthous Ulcers - A discussion about these disorders and their causes. Recurrent Aphthous Stomatitis and Perceived Stress - A research project investigating the relationship between RAS and perceived stress. Mouth Ulcers - Community for sufferers. Includes a causes survey and a treatment survey as well as an informative public message board. WebMD - Oral Health Guide - Find information, prevention and treatment for canker sores. NHS Choices: Mouth Ulcer - Provides information on the different types of ulcer and details of symptoms, causes, diagnosis, treatment, complications and prevention. Patient UK: Oral Ulceration - Factsheet on this condition including presentation, aetiology, local and systemic causes, examinations and management.