diff --git a/ucf_thesis/references.bib b/ucf_thesis/references.bib
index dc8cc54..5b3ffe4 100755
--- a/ucf_thesis/references.bib
+++ b/ucf_thesis/references.bib
@@ -14,6 +14,14 @@ @ARTICLE{Lax
  YEAR={1968},
  PAGES={467-490}
  }
+@ARTICLE{ZS,
+ AUTHOR = "{Zakharov, V.E., Shabat, A.B.}",
+ TITLE = "{Exact theory of two-dimensional self-focusing and one-dimensional self-modulation of waves in nonlinear media}",
+ JOURNAL = {Soviet Physics JETP},
+ VOLUME={34},
+ YEAR={1972},
+ PAGES={62-69}
+ }
 @ARTICLE{ZK,
  AUTHOR = "{Zabusky, N.J., \& Kruskal, M.D.}",
  TITLE = "{Interactions of 'solitons' in a collisionless plasma and the recurrence of initial states}",