update the bookdown guide book
diff --git a/docs/bookdown_example/02-bootstrap_in_gitbook.Rmd b/docs/bookdown_example/02-bootstrap_in_gitbook.Rmd
index 27d1bb4..3172d41 100644
--- a/docs/bookdown_example/02-bootstrap_in_gitbook.Rmd
+++ b/docs/bookdown_example/02-bootstrap_in_gitbook.Rmd
@@ -25,7 +25,7 @@
```
## Epub
-Right now, it's impossible to load addition CSS through HTML dependency (due to a setting in rmarkdown). I will file an issue in `rmarkdown` and see if this is something that can be changed. In the mean time, to use bootstrap tables in Epub, you will have to manually load [this stylesheet](https://github.com/haozhu233/kableExtra/blob/master/inst/bootstrapTable-3.3.7/bootstrapTable.min.css) by putting it to a CSS file (such as "style.css") and load it in `_output.yml`. For example,
+Right now, it's impossible to load addition CSS through HTML dependency and this mechanism exists for a reason ( [See this issue I filed](https://github.com/rstudio/rmarkdown/issues/1457) ). You will have to manually load [this stylesheet](https://github.com/haozhu233/kableExtra/blob/master/inst/bootstrapTable-3.3.7/bootstrapTable.min.css) by putting it to a CSS file (such as "style.css") and load it in `_output.yml`. For example,
```
bookdown::epub_book: