U.S. National Library of Medicine, "Ankylosing spondylitis" http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001457/ Spondylitis U.S. National Library of Medicine, "Ankylosing Spondylitis" Ankylosing Spondylitis U.S. National Library of Medicine, "Ankylosing spondylitis" U.S. National Library of Medicine, "Ankylosing Spondylitis" U.S. National Library of Medicine, "Ankylosing Spondylitis" U.S. National Library of Medicine, "Ankylosing Spondylitis" ankylosing spondylitis http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001457/ U.S. National Library of Medicine, "Ankylosing spondylitis" chronic illness Ankylosing spondylitis: PubMed Health U.S. National Library of Medicine, "Ankylosing spondylitis" ankylosing spondylitis ankylosing spondylitis U.S. National Library of Medicine, "Ankylosing Spondylitis" Ankylosing Spondylitis Ankylosing spondylitis: PubMed Health