Return most recent value using proc SQL in SAS -

i'm looking return recent result letter_source "ccma", based on date letter_type "p29".

basically need know date of last "ccma" letter accounts have had "p29" letter. ccma letter can date long it's recent, p29 must within specific time period.

so far code is:

proc sql;    select distinct       account_no        account_no      ,letter_date   letter_date      ,letter_type   letter_type      ,source        letter_source    uulster.perm_aura_letters    letter_type="p29"      , letter_date >= '01jul2015'd , letter_date <= '09jul2015'd    order letter_date, letter_type; quit; 

please help?

proc sql; select * (select distinct         account_no      account_no         ,letter_date    letter_date         ,letter_type    letter_type         ,source         letter_source         uulster.perm_aura_letters         letter_type="p29"         , letter_source contains "ccma"         , letter_date >= '01jul2015'd , letter_date <= '09jul2015'd) having letter_date=max(letter_date) order letter_date, letter_type ; quit;