Recently when i read lifco's nithayanushtanakramam, it is written that apasthamba and bodayana are the sutras for rig vedha whereas in another book titled " sandhayavandanam" released by sri thillaisthanam swamy kainkarya sabha it was written as asvalayana sutra and katyayana are the sutras for rig vedha . Can any one tell which is correct. And explain how to identify the sutras for rig vedha.