added ref to regression

doc/pub/Regression/html/Regression.html

@@ -310,7 +310,7 @@ MathJax.Hub.Config({
 <center>[2] <b>Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University</b></center>
 <br>
 <p>
-<center><h4>Sep 13, 2019</h4></center> <!-- date -->
+<center><h4>Dec 18, 2019</h4></center> <!-- date -->
 <br>
 <p>
 <!-- !split --><br><br><br><br><br><br><br><br><br><br>
@@ -1951,7 +1951,7 @@ with \( t \) a finite positive number.
 <p>
 We see that Ridge regression is nothing but the standard
 OLS with a modified diagonal term added to \( \boldsymbol{X}^T\boldsymbol{X} \). The
-consequences, in particular for our discussion of the bias-variance
+consequences, in particular for our discussion of the bias-variance tradeoff 
 are rather interesting.
 
 <p>
@@ -3845,6 +3845,9 @@ sets. However, if a method has high variance  then small changes in
 the training data can result in large changes in the model. In general, more
 flexible statistical methods have higher variance.
 
+<p>
+You may also find this recent <a href="https://www.pnas.org/content/116/32/15849" target="_blank">article</a> of interest.
+
 <p>
 <!-- !split --><br><br><br><br><br><br><br><br><br><br>