Try this:
<!DOCTYPE WEEKDAYS[
<!ELEMENT WEEKDAYS (WEEKDAY+)>
<!ELEMENT WEEKDAY EMPTY>
<!ATTLIST WEEKDAY DAY
("SUNDAY"|"MONDAY"|"TUESDAY"|"WEDNESDAY"|"THURSDAY"|"FRIDAY"|"SATURDAY")
#IMPLIED>
]>
<WEEKDAYS>
<WEEKDAY DAY="SUNDAY"/>
<WEEKDAY DAY="FRIDAY"/>
</WEEKDAYS>
Paul Prescod