1. Agency for Healthcare Research and Quality (2019). Clinical Classifications Software (CCS) for ICD-10-PCS (beta version). Healthcare Cost and Utilization Project (HCUP). Retrieved from: www.hcup-us.ahrq.gov/toolssoftware/ccs10/ccs10.jsp. Accessed.
2. Alcohol Drug Abuse Institute (ADAI) (2018). Washington State Opioid/Major Drug Interactive Data: Methamphetamine trends across Washington state. Retrieved from: http://adai.uw.edu/wadata/methamphetamine.htm. Accessed.
3. Nonmedical use of prescription stimulants among college students: Associations with attention-deficit-hyperactivity disorder and polydrug use;Arria;Pharmacotherapy,2008
4. Can differences in the type, nature or amount of polysubstance use explain the increased risk of non-fatal overdose among psychologically distressed people who inject drugs?;Betts;J Drug alcohol dependence,2015
5. Caleb Banta-Green, S. K., Ohta, J., Taylor, M., Sylla, L., Tinsley, J., Smith, R., Couper, F., Harruff, R., Freng, S., & Von Derau, K. (2015). 2015 Drug Use Trends for King County, Washington. Retrieved from: http://adai.uw.edu/pubs/pdf/2015drugusetrends.pdf. Accessed 2/26/2019 2019.