Fix typo.

etc/TUTORIAL

@@ -575,7 +575,7 @@ is always part of some buffer.
 
 >> Type C-x 1 to get rid of the buffer list.
 
-When you have several buffers, only of of them is "current" at any
+When you have several buffers, only one of them is "current" at any
 time.  That buffer is the one you edit.  If you want to edit another
 buffer, you need to "switch" to it.  If you want to switch to a buffer
 that corresponds to a file, you can do it by visiting the file again

src/coding.c

@@ -2685,7 +2685,7 @@ encode_coding_iso2022 (coding, source, destination, src_bytes, dst_bytes)
 
 /* Macros to decode or encode a character of Big5 in BIG5.  B1 and B2
    are the 1st and 2nd position-codes of Big5 in BIG5 coding system.
-   C1 and C2 are the 1st and 2nd position-codes of of Emacs' internal
+   C1 and C2 are the 1st and 2nd position-codes of Emacs' internal
    format.  CHARSET is `charset_big5_1' or `charset_big5_2'.  */
 
 /* Number of Big5 characters which have the same code in 1st byte.  */