American Diabetes Assosciation
http://www.diabetes.org/diabetes-basics/symptoms/?loc=DropDownDB-symptoms
Mayo Clinic
http://www.mayoclinic.com/health/diabetes/DS01121/DSECTION=symptoms
MedicineNet
http://www.medicinenet.com/diabetes_mellitus/page7.htm#what_are_diabetes_symptoms
WebMD
http://diabetes.webmd.com/diabetes-blurred-vision
PubMed
http://www.ncbi.nlm.nih.gov/pubmed/6400426
Medical News Today