Bibliography (13):

1. Testing hypotheses about direction of causation using cross-sectional family data

2. Correlation and Causation in the Study of Personality

3. Causal Inference and Observational Research: The Utility of Twins

4. Distinguishing genetic correlation from causation across 52 diseases and complex traits

5. Mendelian Randomization accounting for correlated and uncorrelated pleiotropic effects using genome-wide summary statistics

6. Proceeding From Observed Correlation to Causal Inference: The Use of Natural Experiments

7. There Is a World Outside of Experimental Designs: Using Twins to Investigate Causation

8. Using Twins to Assess What Might Have Been: The Co-twin Control Design

9. The continuing value of twin studies in the omics era

10. Critical need for family-based, quasi-experimental designs in integrating genetic and social science research

11. Wikipedia Bibliography:

    1. https://en.wikipedia.org/wiki/Multivariate_statistics  :

       https://en.wikipedia.org/wiki/Multivariate_statistics

    2. Twin study

    3. Reliability (statistics)