Adding new partitions to a table with existing partitions and indexes

 HiI have a table with following DDL

CREATE TABLE "WAREHOUSE"."WMEAS_DAILY_MEASURED_VOLUME" (............)

TABLESPACE "DLY_MEAS_VOL_DP_MAXVALUE"

PARTITION BY RANGE ("GAS_DAY") 

PARTITION "P_2012" VALUES LESS THAN(TO_DATE(' 2013-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')) 

TABLESPACE"DLY_MEAS_VOL_DATA_2012" ,

PARTITION "P_2013" VALUES LESS THAN(TO_DATE(' 2014-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')) 

TABLESPACE"DLY_MEAS_VOL_DATA_2013" , 

PARTITION "P_MAXVALUE" VALUES LESS THAN(MAXVALUE) 

TABLESPACE "DLY_MEAS_VOL_DP_MAXVALUE" 

This tables have indexes too and they are partitioned too.

I need to add two more yearly partitions 2014 and 2015.