fix some markup errors
diff --git a/Doc/lib/libbase64.tex b/Doc/lib/libbase64.tex
index d7eccbd..23b74f0 100644
--- a/Doc/lib/libbase64.tex
+++ b/Doc/lib/libbase64.tex
@@ -85,7 +85,7 @@
letter O (oh), and for optional mapping of the digit 1 (one) to either
the letter I (eye) or letter L (el). The optional argument
\var{map01} when not \code{None}, specifies which letter the digit 1 should
-be mapped to (when map01 is not \var{None}, the digit 0 is always
+be mapped to (when \var{map01} is not \code{None}, the digit 0 is always
mapped to the letter O). For security purposes the default is
\code{None}, so that 0 and 1 are not allowed in the input.
diff --git a/Doc/lib/liblogging.tex b/Doc/lib/liblogging.tex
index 4bb0595..f9c1d72 100644
--- a/Doc/lib/liblogging.tex
+++ b/Doc/lib/liblogging.tex
@@ -1531,7 +1531,7 @@
\var{exc_info} is the exception tuple obtained by calling
\function{sys.exc_info() }(or \constant{None}, if no exception information
is available). The \var{func} is the name of the function from which the
-logging call was made. If not specified, it defaults to \var{None}.
+logging call was made. If not specified, it defaults to \code{None}.
\versionchanged[\var{func} was added]{2.5}
\end{classdesc}
diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
index d7b8858..66cc476 100644
--- a/Doc/lib/libstdtypes.tex
+++ b/Doc/lib/libstdtypes.tex
@@ -1466,7 +1466,7 @@
\item[(5)] \function{setdefault()} is like \function{get()}, except
that if \var{k} is missing, \var{x} is both returned and inserted into
-the dictionary as the value of \var{k}. \var{x} defaults to \var{None}.
+the dictionary as the value of \var{k}. \var{x} defaults to \code{None}.
\item[(6)] \function{popitem()} is useful to destructively iterate
over a dictionary, as often used in set algorithms. If the dictionary
@@ -1818,7 +1818,7 @@
expection that occurred should be suppressed. If an exception
occurred while executing the body of the \keyword{with} statement, the
arguments contain the exception type, value and traceback information.
- Otherwise, all three arguments are \var{None}.
+ Otherwise, all three arguments are \code{None}.
Returning a true value from this method will cause the \keyword{with}
statement to suppress the exception and continue execution with the
diff --git a/Doc/lib/libxmlrpclib.tex b/Doc/lib/libxmlrpclib.tex
index 7af9e76..1aa2dd5 100644
--- a/Doc/lib/libxmlrpclib.tex
+++ b/Doc/lib/libxmlrpclib.tex
@@ -287,7 +287,7 @@
Create an object used to boxcar method calls. \var{server} is the
eventual target of the call. Calls can be made to the result object,
-but they will immediately return \var{None}, and only store the
+but they will immediately return \code{None}, and only store the
call name and parameters in the \class{MultiCall} object. Calling
the object itself causes all stored calls to be transmitted as
a single \code{system.multicall} request. The result of this call