Corrections for a/an in code comments and documentation
diff --git a/Mac/README b/Mac/README
index 6e08fdc..b4c6b7f 100644
--- a/Mac/README
+++ b/Mac/README
@@ -126,7 +126,7 @@
To build a universal binary that includes a 64-bit architecture, you must build
on a system running OS X 10.5 or later. The ``all`` and ``64-bit`` flavors can
-only be built with an 10.5 SDK because ``ppc64`` support was only included with
+only be built with a 10.5 SDK because ``ppc64`` support was only included with
OS X 10.5. Although legacy ``ppc`` support was included with Xcode 3 on OS X
10.6, it was removed in Xcode 4, versions of which were released on OS X 10.6
and which is the standard for OS X 10.7. To summarize, the