added index entries for __*__ identifiers
diff --git a/Doc/ref/ref8.tex b/Doc/ref/ref8.tex
index 1ae61ed..a9e688a 100644
--- a/Doc/ref/ref8.tex
+++ b/Doc/ref/ref8.tex
@@ -31,6 +31,7 @@
 is identical to that of a complete program; each statement is executed
 in the name space of \verb@__main__@.
 \index{interactive mode}
+\bimodindex{__main__}
 
 Under {\UNIX}, a complete program can be passed to the interpreter in
 three forms: with the {\bf -c} {\it string} command line option, as a