extra changes for footnote with threeparttable
diff --git a/docs/awesome_table_in_pdf.Rmd b/docs/awesome_table_in_pdf.Rmd
index 2faba1b..8e7d092 100644
--- a/docs/awesome_table_in_pdf.Rmd
+++ b/docs/awesome_table_in_pdf.Rmd
@@ -318,6 +318,21 @@
 # Not evaluated. The code above should have the same result as the first example in this section.
 ```
 
+Note that `kable` has a relatively special feature to handle `align` and it may bring troubles to you if you are not using it correctly. In the documentation of the `align` argument of `kable`, it says:
+
+> If `length(align) == 1L`, the string will be expanded to a vector of individual letters, e.g. `'clc'` becomes `c('c', 'l', 'c')`, **unless the output format is LaTeX**.
+
+For example, 
+```{r, eval=F}
+kable(mtcars[1:2, 1:2], "latex", align = c("cl"))
+# \begin{tabular}{l|cl|cl}  # Note the column alignment here
+# \hline
+#   & mpg & cyl\\
+# ...
+```
+
+LaTeX, somehow shows surprisingly high tolerance on that, which is quite unusual. As a result, it won't throw an error if you are just using `kable` to make some simple tables. However, when you use `kableExtra` to make some advanced modification, it will start to throw some bugs. As a result, please try to form a habbit of using a vector in the `align` argument for `kable` (tip: you can use `rep` function to replicate elements. For example, `c("c", rep("l", 10))`). 
+
 ## Row indentation
 Unlike `group_rows()`, which will insert a labeling row, sometimes we want to list a few sub groups under a total one. In that case, `add_indent()` is probably more apporiate. 
 For advanced users, you can even define your own css for the group labeling.
@@ -347,6 +362,8 @@
   collapse_rows(1:2)
 ```
 
+
+
 # Table Footnote
 
 > Now it's recommended to use the new `footnote` function instead of `add_footnote` to make table footnotes. 
@@ -396,6 +413,14 @@
            footnote_as_chunk = T)
 ```
 
+If your table footnote is very long, please consider to put your table in a `ThreePartTable` frame. Note that, in kableExtra version <= 0.7.0, we were using `threeparttable` but since kableExtra 0.8.0, we start to use `ThreePartTable` from `threeparttablex` instead. `ThreePartTable` supports both the `longtable` and `tabu` environments. 
+
+```{r}
+kable(dt, "latex", align = "c", booktabs = T, caption = "s") %>%
+  footnote(general = "Here is a very very very very very very very very very very very very very very very very very very very very long footnote", 
+           threeparttable = T)
+```
+
 # LaTeX Only Features
 ## Table on a Landscape Page
 Sometimes when we have a wide table, we want it to sit on a designated landscape page. The new function `landscape()` can help you on that. Unlike other functions, this little function only serves LaTeX and doesn't have a HTML side.