References
                                                        1 California Environmental Protection Agency.
                                                            Identification of Environmental Tobacco Smoke as a Toxic Air
                                                            Contaminant. Executive Summary. June 2005. 
                                                        2 U.S. Department of Health and Human Services.
                                                            The Health Consequences of Involuntary Exposure to Tobacco
                                                            Smoke: A Report of the Surgeon General. U.S. Department of
                                                            Health and Human Services, Centers for Disease Control and
                                                            Prevention, National Center for Chronic Disease Prevention
                                                            and Health Promotion, Office on Smoking and Health, 2006.
                                                        
                                                        3 Office on Smoking and Health, National Center
                                                            for Chronic Disease Prevention and Health Promotion, Centers
                                                            For Disease Control and Prevention.
                                                            http://www.cdc.gov/tobacco
                                                        4 Office on Smoking and Health, National Center
                                                            for Chronic Disease Prevention and Health Promotion -
                                                            http://www.cdc.gov/tobacco/data_statistics/fact_sheets/secondhand_smoke/general_facts/index.htm