diff --git a/paper.bib b/paper.bib
index 4172da6..dc20995 100644
--- a/paper.bib
+++ b/paper.bib
@@ -202,6 +202,17 @@ @article{2017_msrk
 	Volume = {86},
 	Year = {2017}}
 
+@article{2018_perturbations,
+  title={Optimal Monotonicity-Preserving Perturbations of a Given {R}unge--{K}utta Method},
+  author={Higueras, Inmaculada and Ketcheson, David I. and Kocsis, Tiham{\'e}r A},
+  journal={Journal of Scientific Computing},
+  volume={76},
+  number={3},
+  pages={1337--1369},
+  year={2018},
+  publisher={Springer},
+	doi={10.1007/s10915-018-0664-3}
+}
 
 @article{conde2018embedded,
   title={Embedded error estimation and adaptive step-size control for optimal explicit strong stability preserving {R}unge--{K}utta methods},