Update README.md

README.md

@@ -37,20 +37,25 @@ const numItems = cat.nItems;
 
 // find the next available item from an input array of stimuli based on a selection method
 
-const stimuli = [{difficulty: -3,  item: 'item1'}, {difficulty: -2,  item: 'item2'}];
+const stimuli = [{difficulty: -3, item: 'item1'}, {difficulty: -2,  item: 'item2'}];
 
 const nextItem = cat.findNextItem(stimuli, 'MFI');
 ```
 
 ## Validations
-### Validation of theta estimate and theta standard error 
-![img.png](img.png)
+### Validation of theta estimate and theta standard error
+Reference software: mirt (Chalmers, 2012)
+![img.png](validation/plots/jsCAT_validation_1.png)
 
 ### Validation of MFI algorithm 
-![img_1.png](img_1.png)
+Reference software: catR (Magis et al., 2017)
+![img_1.png](validation/plots/jsCAT_validation_2.png)
 
 
 ## References
+Chalmers, R. P. (2012). mirt: A multidimensional item response theory package for the R environment. Journal of Statistical Software.
+
+Magis, D., & Barrada, J. R. (2017). Computerized adaptive testing with R: Recent updates of the package catR. Journal of Statistical Software, 76, 1-19.
 
 Lucas Duailibe, irt-js, (2019), GitHub repository, https://github.com/geekie/irt-js