ORDER BY problem

This query selects the most recent advertisement (in table
wha_listing) for all properties (in table wha_property) and returns
the sales agency (in table wha_agency), as well as other data. The
query works as expected.

SELECT DISTINCT ON (property_id)
property_id, date, wha_property.propnum, wha_street.street_name,
wha_suburb.suburb_name, wha_agent.first_name, wha_agent.last_name,
wha_agency.name
FROM wha_listing, wha_agent, wha_agency, wha_property, wha_street,
wha_suburb
WHERE wha_suburb.id = wha_street.suburb_id
AND wha_street.id = wha_property.street_id
AND wha_property.id = property_id
AND wha_agency.id = wha_agent.agency_id
AND wha_agent.id = agent_id
AND wha_listing.date >= "2009-01-01" ORDER BY wha_listing.property_id,
wha_listing.date DESC;

I need the resulting list to be sorted by wha_agency.name

Can I do this by adding something to this query?

TIA

Michael Rowan
mike(dot)rowan(at)internode(dot)on(dot)net

11 Kingscote Street
ALBERTON
South Australia 5014

tel 618 8240 3993