BEGIN:VCALENDAR
BEGIN:VEVENT
DESCRIPTION
 :Monday of week number 20 (where the default start of the week is Monday)\,
 forever:
DTSTART
 :19970512T090000
RRULE   
 :FREQ=YEARLY;INTERVAL=1;COUNT=10;BYDAY=MO;BYWEEKNO=20
X-EXPECT-NUMEVENTS: 11
END:VEVENT
END:VCALENDAR