Include citation information

[EeethB]

ROpenSci standards referencing citation information: https://devguide.ropensci.org/building.html#citation-file

Needs to include both citations of Bretz et al (2011) & how to cite the package for users. Do we need to cite {gMCP} too? Probably

[xidongdxi]

Key references for now. We probably will expand later.
Bretz, F., Maurer, W., Brannath, W., & Posch, M. (2009). A graphical approach to sequentially rejective multiple test procedures. Statistics in medicine, 28(4), 586-604.
Bretz, F., Posch, M., Glimm, E., Klinglmueller, F., Maurer, W., & Rohmeyer, K. (2011). Graphical approaches for multiple comparison procedures using weighted Bonferroni, Simes, or parametric tests. Biometrical Journal, 53(6), 894-913.
Rohmeyer K, Klinglmueller F (2020). gMCP: Graph Based Multiple Test Procedures. R package version 0.8-15, https://cran.r-project.org/package=gMCP.
Lu, K. (2016). Graphical approaches using a Bonferroni mixture of weighted Simes tests. Statistics in Medicine, 35(22), 4041-4055.
Xi, D., Glimm, E., Maurer, W., & Bretz, F. (2017). A unified framework for weighted parametric multiple test procedures. Biometrical Journal, 59(5), 918-931.
Xi, D., & Bretz, F. (2019). Symmetric graphs for equally weighted tests, with application to the Hochberg procedure. Statistics in Medicine, 38(27), 5268-5282.
Brannath, W., Bretz, F., Maurer, W., & Sarkar, S. (2009). Trimmed weighted Simes' test for two one‐sided hypotheses with arbitrarily correlated test statistics. Biometrical Journal: Journal of Mathematical Methods in Biosciences, 51(6), 885-898.