Update README.md

Author: ehsanx

README.md

@@ -39,10 +39,10 @@ simmsm(subjects = 2500, tpoints = 10, psi = 0.3, n = 5)
 
 ### Original Paper
 - [x] Young J.G., Hernan M.A., Picciotto S., and Robins J.M. [Relation between three classes of structural models for the effect of a time-varying exposure on survival](http://link.springer.com/article/10.1007/s10985-009-9135-3). Lifetime Data Analysis, 16(1):71-84, 2010. 
-- [] Young, Jessica G., et al. Simulation from structural survival models under complex time-varying data structures. JSM proceedings, section on statistics in epidemiology. American Statistical Association, Denver, CO (2008)
+- [ ] Young, Jessica G., et al. Simulation from structural survival models under complex time-varying data structures. JSM proceedings, section on statistics in epidemiology. American Statistical Association, Denver, CO (2008)
 
 ### Follow-up References
-- [] Ali R.A., Ali M.A., and Wei Z. [On computing standard errors for marginal structural cox models](http://link.springer.com/article/10.1007%2Fs10985-013-9255-7). Lifetime data analysis, pages 1–26, 2013. doi: 10.1007/s10985-013-9255-7.
-- [] Xiao Y., Abrahamowicz M., and Moodie E.E.M. [Accuracy of conventional and marginal structural Cox model estimators: A simulation study](http://www.degruyter.com/view/j/ijb.2010.6.2/ijb.2010.6.2.1208/ijb.2010.6.2.1208.xml?format=INT). The International Journal of Biostatistics, 6(2):1–28, 2010. 
-- [] Karim, M. E.; Petkau, J.; Gustafson, P.; Platt, R.; Tremlett, H. and BeAMS study group. [Comparison of Statistical Approaches Dealing with Time-dependent Confounding in Drug Effectiveness Studies](http://smm.sagepub.com/content/early/2016/09/21/0962280216668554.abstract). Statistical Methods in Medical Research. First published online: September 21. doi: 10.1177/0962280216668554
-- [] Karim, M. E.; Petkau, J.; Gustafson, P.; Tremlett, H. and BeAMS study group. [On the application of statistical learning approaches to construct inverse probability weights in marginal structural Cox models: hedging against weight-model misspecification](http://www.tandfonline.com/toc/lssp20/current). Communications in Statistics - Simulation and Computation (In Press).
+- [ ] Ali R.A., Ali M.A., and Wei Z. [On computing standard errors for marginal structural cox models](http://link.springer.com/article/10.1007%2Fs10985-013-9255-7). Lifetime data analysis, pages 1–26, 2013. doi: 10.1007/s10985-013-9255-7.
+- [ ] Xiao Y., Abrahamowicz M., and Moodie E.E.M. [Accuracy of conventional and marginal structural Cox model estimators: A simulation study](http://www.degruyter.com/view/j/ijb.2010.6.2/ijb.2010.6.2.1208/ijb.2010.6.2.1208.xml?format=INT). The International Journal of Biostatistics, 6(2):1–28, 2010. 
+- [ ] Karim, M. E.; Petkau, J.; Gustafson, P.; Platt, R.; Tremlett, H. and BeAMS study group. [Comparison of Statistical Approaches Dealing with Time-dependent Confounding in Drug Effectiveness Studies](http://smm.sagepub.com/content/early/2016/09/21/0962280216668554.abstract). Statistical Methods in Medical Research. First published online: September 21. doi: 10.1177/0962280216668554
+- [ ] Karim, M. E.; Petkau, J.; Gustafson, P.; Tremlett, H. and BeAMS study group. [On the application of statistical learning approaches to construct inverse probability weights in marginal structural Cox models: hedging against weight-model misspecification](http://www.tandfonline.com/toc/lssp20/current). Communications in Statistics - Simulation and Computation (In Press).