Update README.md

Author: ZebinYang

README.md

@@ -13,3 +13,16 @@ conda install r-base
 conda install r-bigsplines
 pip install git+https://github.com/ZebinYang/simtree.git
 ```
+
+# Contact:
+If you find any bugs or have any suggestions, please contact us via email: [email protected] or [email protected].
+
+# Citations:
+```latex
+@article{sudjianto2021single,
+	author  = {Sudjianto, Agus and Yang, Zebin and Zhang, Aijun},
+	title   = {Single-Index Model Tree},
+	journal = {IEEE Transactions on Knowledge and Data Engineering},
+	year    = {2021},
+	url     = {http://jmlr.org/papers/v22/20-058.html}
+}