Restore part of doc

passes/equiv/equiv_opt.cc

diff --git a/passes/equiv/equiv_opt.cc b/passes/equiv/equiv_opt.cc
index d13e46c..ec12004 100644
--- a/passes/equiv/equiv_opt.cc
+++ b/passes/equiv/equiv_opt.cc
@@ -32,7 +32,8 @@
 		log("\n");
 		log("    equiv_opt [options] [command]\n");
 		log("\n");
-		log("This command checks circuit equivalence before and after an optimization pass.\n");
+		log("This command uses temporal induction to check circuit equivalence before and\n");
+		log("after an optimization pass.\n");
 		log("\n");
 		log("    -run <from_label>:<to_label>\n");
 		log("        only run the commands between the labels (see below). an empty\n");