-The format of @var{Iinput} is automatically detected, except that the
-character encoding of old system files cannot always be guessed
-correctly. Use @code{-e @var{encoding}} to specify the encoding in this
-case.
+The format of @var{Iinput} is automatically detected, when possible.
+The character encoding of old SPSS system files cannot always be
+guessed correctly, and SPSS/PC+ system files do not include any
+indication of their encoding. Use @code{-e @var{encoding}} to specify
+the encoding in this case.