name the common home port of the usrc washington and uscgc thetis ?
SELECT DISTINCT var_uri where brack_open dbr_USRC_Washington_ attr_open 1833 attr_close dbo_homeport var_uri sep_dot dbr_USCGC_Thetis_ attr_open WMEC-910 attr_close dbo_homeport var_uri brack_close