add citations to DESCRIPTION and package man page

DESCRIPTION

@@ -1,17 +1,25 @@
 Package: spduration
 Title: Split-Population Duration (Cure) Regression
 Version: 0.16.0
-Date: 2017-04-10
+Date: 2017-04-11
 Authors@R: c(
-    person("Andreas", "Beger", role = c("aut", "cre"), email = "adbeger@gmail.com"),
-    person("Daina", "Chiba", role = c("aut"), email = "dchiba@essex.ac.uk"),
-    person("Daniel", "Hill", role = c("aut"), email = "dwhill@uga.edu"),
-    person("Nils", "Metternich", role = c("aut"), email = "n.metternich@ucl.ac.uk"),
-    person("Shahryar", "Minhas", role = c("aut"), email = "hermes829@gmail.com"),
-    person("Michael", "Ward", role = c("cph"), email = "michael.don.ward@gmail.com")
+    person("Andreas", "Beger", , "adbeger@gmail.com", c("aut", "cre")),
+    person("Daina", "Chiba", , "dchiba@essex.ac.uk", "aut"),
+    person("Daniel W.", "Hill, Jr.", , "dwhill@uga.edu", "aut"),
+    person("Nils W.", "Metternich", , "n.metternich@ucl.ac.uk", "aut"),
+    person("Shahryar", "Minhas", , "hermes829@gmail.com", "aut"),
+    person("Michael D.", "Ward", , "michael.don.ward@gmail.com", c("aut", "cph"))
     )
-Description: Functions for estimating split-duration regression models and
-    various associated generic function methods.
+Description: An implementation of split-population duration regression models. 
+    Unlike regular duration models, split-population duration models are
+    mixture models that accommodate the presence of a sub-population that is 
+    not at risk for failure, e.g. cancer patients who have been cured by 
+    treatment. This package implements Weibull and Loglogistic forms for the 
+    duration component, and focuses on data with time-varying covariates. 
+    These models were originally formulated in Boag (1949) 
+    <http://www.jstor.org/stable/2983694> and Berkson and Gage (1952) 
+    <http://www.jstor.org/stable/2281318>, and extended in Schmidt and Witte 
+    (1989) <doi:10.1016/0304-4076(89)90034-1>.
 Depends:
     R (>= 3.1.2)
 License: GPL-3

NEWS

@@ -1,9 +1,10 @@
-# spduration 0.16.0 (2017-04-02)
+# spduration 0.16.0 (2017-04-11)
 
 * separationplot.spdur -> sepplot. `separationplot` is a standalone function so change the `spdur` version to a simple wrapper. 
-* Clean up NAMESPACE. Moved `stats` to imported package in description and removed all associated explicit namespace generic imports. 
-* Add package vignette.
+* Cleaned up NAMESPACE. Moved `stats` to imported package in description and removed all associated explicit namespace generic imports. 
+* Added package vignette.
 * Added file `init.c` with calls to `R_registerRoutines()` and `R_useDynamicSymbols()`; also use `.registration=TRUE` in `useDynLib` in `NAMESPACE`. R-devel (and R 3.4.0 in the future) `R CMD check` issues a NOTE for registration of routines, this is to avoid that note.  
+* Updated DESCRIPTION and added references.
 
 # spduration 0.15.1 (2016-05-12)
 

NEWS.md

@@ -1,9 +1,10 @@
-# spduration 0.16.0 (2017-04-02)
+# spduration 0.16.0 (2017-04-11)
 
 * separationplot.spdur -> sepplot. `separationplot` is a standalone function so change the `spdur` version to a simple wrapper. 
-* Clean up NAMESPACE. Moved `stats` to imported package in description and removed all associated explicit namespace generic imports. 
-* Add package vignette.
+* Cleaned up NAMESPACE. Moved `stats` to imported package in description and removed all associated explicit namespace generic imports. 
+* Added package vignette.
 * Added file `init.c` with calls to `R_registerRoutines()` and `R_useDynamicSymbols()`; also use `.registration=TRUE` in `useDynLib` in `NAMESPACE`. R-devel (and R 3.4.0 in the future) `R CMD check` issues a NOTE for registration of routines, this is to avoid that note.  
+* Updated DESCRIPTION and added references.
 
 # spduration 0.15.1 (2016-05-12)
 

R/spduration-package.R

@@ -16,8 +16,18 @@
 #'     display of model fit. 
 #' 
 #' @references
+#'     Boag, J.W. 1949. ``Maximum Likelihood Estimates of the Proportion of 
+#'       Patients Cured by Cancer Therapy.'' <http://www.jstor.org/stable/2983694>
+#' 
+#' 	   Berkson, J. and Gage, R.P. ``Survival Curve for Cancer Patients Following 
+#' 	     Treatment.'' <http://www.jstor.org/stable/2281318>
+#' 
 #'     Leisch, Friedrich. 2009. ``Creating R Packages: A Tutorial.''
-#'     
+#' 
+#'     Schmidt, Peter and Witte, Ann Dryden. 1989. ``Predicting Criminal 
+#'       Recidivism Using "Split Population" Survival Time Models.'' 
+#'       <doi:10.1016/0304-4076(89)90034-1>    
+#' 
 #'     Svolik, Milan. 2008. ``Authoritarian Reversals and Democratic 
 #'         Consolidation.'' American Political Science Review.
 #'