adding this again

docs/src/refs.bib

@@ -491,6 +491,19 @@ @Article{Morris1997
   publisher = {Elsevier BV},
 }
 
+@article{Morris2000,
+  author = {Morris, Joseph P.},
+  title = {Simulating surface tension with smoothed particle hydrodynamics},
+  journal = {International Journal for Numerical Methods in Fluids},
+  volume = {33},
+  number = {3},
+  pages = {333-353},
+  keywords = {interfacial flow, meshless methods, surface tension},
+  doi = {https://doi.org/10.1002/1097-0363(20000615)33:3<333::AID-FLD11>3.0.CO;2-7},
+  year = {2000}
+}
+
+
 @InProceedings{Mueller2003,
   author    = {M{\"u}ller, Matthias and Charypar, David and Gross, Markus},
   booktitle = {Proceedings of the 2003 ACM SIGGRAPH/Eurographics Symposium on Computer Animation},