1 files changed, 12 insertions, 0 deletions
diff --git a/docs/source/references.bib b/docs/source/references.bib
index 0fb077ec..7b1e876b 100644
--- a/docs/source/references.bib
+++ b/docs/source/references.bib
@@ -197,6 +197,18 @@
   Url                      = {https://archive.org/details/DTIC_ADA026294}
 }
 
+@article{Ruffhead2016,
+    author = {A. C. Ruffhead},
+    title = {Introduction to multiple regression equations in datum transformations and their reversibility},
+    journal = {Survey Review},
+    volume = {50},
+    number = {358},
+    pages = {82-90},
+    year  = {2016},
+    publisher = {Taylor & Francis},
+    doi = {10.1080/00396265.2016.1244143},
+}
+
 @Book{Snyder1993,
   Title                    = {Flattening the Earth},
   Author                   = {J. P. Snyder},