John's fixes to documentation

docs-source/usersguide/library.rst

@@ -2614,6 +2614,9 @@ nanometers.  We could just as easily specify it in different units:
 
 The use of units in OpenMM is discussed in the next section.
 
+
+.. _units-and-dimensional-analysis:
+
 Units and dimensional analysis
 ==============================
 

docs-source/usersguide/references.bib

@@ -378,6 +378,16 @@
    type = {Journal Article}
 }
 
+@article{Srinivasan1999
+   author = {Srinivasan, J and Trevathan, M. W. and Beroza, P. and Case, D. A.},
+   title = {Application of a pairwise generalized {Born} model to proteins and nucleic acids: inclusion of salt effects},
+   journal = {Theor. Chem. Acc.},
+   volume = {101},
+   pages = {426-434},
+   year = {1999},
+   type = {Journal Article}
+}
+
 @article{Thole1981
    author = {Thole, B. T.},
    title = {Molecular polarizabilities calculated with a modified dipole interaction},