1. Instrumental variable methods in clinical research
Emilia Bagiella, PhD, Tara Karamlou, MD, Helena Chang, MS, John Spivack, PhD 
The Journal of Thoracic and Cardiovascular Surgery 
Volume 150, Issue 4, Pages (October 2015)
DOI: /j.jtcvs
Copyright © 2015 The American Association for Thoracic Surgery Terms and Conditions

2. Figure 1 Causal pathway with instrumental variable.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /j.jtcvs )
Copyright © 2015 The American Association for Thoracic Surgery Terms and Conditions

3. Causal pathway with instrumental variable.
The Journal of Thoracic and Cardiovascular Surgery  , DOI: ( /j.jtcvs )
Copyright © 2015 The American Association for Thoracic Surgery Terms and Conditions