Logic on Oracle Tree

Output from the query :

STARTING_REF_ID REF_LABEL

           501 article 501           502 par 502,article 501           503 (503,par 502,article 501

Expected result:

STARTING_REF_ID REF_LABEL

           501 article 501           502 article 501,par 502           503 article 501,par 502,(503,