diff --git a/paper.bib b/paper.bib
index 86c9b0e..24f1d40 100644
--- a/paper.bib
+++ b/paper.bib
@@ -60,9 +60,8 @@ @article{ALONSOTRISTAN20112729
 
 @BOOK{HPEH,
   TITLE = {Hydropower Engineering Handbook},
-  SUBTITLE = {},
   AUTHOR = {Gulliver, John S. and Arndt, Roger E.A.},
-  YEAR = {1991}, % I looked it up
+  YEAR = {1991},
   PUBLISHER = {McGraw-Hill, Inc.},
 }