diff --git a/R/footnote.R b/R/footnote.R
index 8863327..5e9201f 100644
--- a/R/footnote.R
+++ b/R/footnote.R
@@ -26,6 +26,9 @@
 #' @param alphabet_title Section header for alphabet footnotes. Default is "".
 #' @param symbol_title Section header for symbol footnotes. Default is "".
 #'
+#' @examples x <- mtcars[1:5, 1:5]
+#' footnote(knitr::kable(dt, "html"), alphabet = c("Note a", "Note b"))
+#'
 #' @export
 footnote <- function(kable_input,
                      general = NULL,
diff --git a/R/footnote_marker.R b/R/footnote_marker.R
index df54339..beb1c4e 100644
--- a/R/footnote_marker.R
+++ b/R/footnote_marker.R
@@ -11,6 +11,11 @@
 #' @param format Either `html` or `latex`. All functions here can read
 #' default value from global option `knitr.table.format`.
 #'
+#' @examples x <- mtcars[1:5, 1:5]
+#' colnames(dt)[1] <- paste0("mpg", footnote_marker_alphabet(2, "html"))
+#' rownames(dt)[2] <- paste0(rownames(dt)[2], footnote_marker_alphabet(1, "html"))
+#' footnote(knitr::kable(dt, "html"), alphabet = c("Note a", "Note b"))
+#'
 #' @export
 footnote_marker_number <- function(x, format) {
   if (missing(format) || is.null(format)) {
diff --git a/R/row_spec.R b/R/row_spec.R
index d58493c..deedf68 100644
--- a/R/row_spec.R
+++ b/R/row_spec.R
@@ -33,7 +33,7 @@
 row_spec <- function(kable_input, row,
                      bold = FALSE, italic = FALSE, monospace = FALSE,
                      color = NULL, background = NULL, align = NULL,
-                     font_size = NULL, angle = NULL, extra_css) {
+                     font_size = NULL, angle = NULL, extra_css = NULL) {
   if (!is.numeric(row)) {
     stop("row must be numeric. ")
   }