mantrena
mantreṇa — by this hymn, or mantra; SB 4.8.54
mantreṇa — mantra; SB 6.19.7
mūla-mantreṇa — with the appropriate basic mantra for worshiping the particular Deity; SB 11.3.50-51
mūla-mantreṇa — with the primary mantras naming each deity; SB 11.27.38-41