Update pstr-vignette.Rmd

Author: yukai-yang

vignettes/pstr-vignette.Rmd

@@ -261,22 +261,4 @@ ret$cfa
 
 ```{r sales, eval=F}
 ret$sales
-```
-
-
-## Citation
-
-If you use the PSTR package in your research, please cite both the software implementation and the underlying methodology.
-
-**Software**
-
-Yang, Y. (2026). PSTR: Panel Smooth Transition Regression Modelling. R package version 2.0.0 (first released in 2017). Available at: https://github.com/yukai-yang/PSTR
-
-**Methodology**
-
-González, A., Teräsvirta, T., van Dijk, D., and Yang, Y. (2005). Panel Smooth Transition Regression Models. EFI Working Paper Series in Economics and Finance, No. 604. Stockholm School of Economics. Revised October 2017. Available at: https://swopec.hhs.se/hastef/papers/hastef0604.pdf
-
-You can obtain the citation information directly from R by running:
-```{r citation}
-citation("PSTR")
 ```