SQL Query tuning help needed

Hi ,

I am working on one sql query tuning and it it taking morethan 100 seconds to retrie the rersults, we have recently gathered DB stats and index rebuild acitivity but still there is no change in execution time. Could anyone please suggest me to perform this query much quicker.

  SELECT usr_grp_id AS usrGrpId
  FROM PUK.VW_USER_GROUP_WORKLIST vw
  WHERE NOT EXISTS (SELECT * FROM (
   (SELECT usa.usr_grp_id,
        usr_entl.criteria_nm,
        usa.srvc_id
   FROM PUK.user_grp_srvc_assoc usa,
         (SELECT DISTINCT ut.usr_id,
          attr.criteria_nm
         FROM PUK.user_tbl ut,
   PUK.user_assgn ua,