diff --git a/blocklist-update.sh b/blocklist-update.sh
index d02a76d..3d7908b 100644
--- a/blocklist-update.sh
+++ b/blocklist-update.sh
@@ -14,6 +14,7 @@ GREP_PATH="/bin/grep"
 
 if [ -f $IPTABLES_PATH ]; then echo "iptables OK"; else echo "Cannot find [ iptables ]. Is it installed? Exiting"; exit 1; fi;
 #hash iptables 2>/dev/null || { echo >&2 "I require iptables but it's not installed.  Aborting."; exit 1; }
+#more in https://stackoverflow.com/questions/592620/how-can-i-check-if-a-program-exists-from-a-bash-script
 if [ -f $IPSET_PATH ]; then echo "ipset OK"; else echo "Cannot find [ ipset ]. Is it installed? Exiting"; exit 1; fi;
 if [ -f $SORT_PATH ]; then echo "sort OK"; else echo "Cannot find [ sort ]. Is it installed? Exiting"; exit 1; fi;
 if [ -f $MAIL_PATH ]; then echo "mail OK"; else echo "Cannot find [ mail ]. Is it installed? Exiting"; exit 1; fi;