dromkara

i am a vaidiki brahmin and i perform sandhyavandanam along with mudras.i want to know the meaning of 24 mudras and 8 uttara mudra , each one of them individually. i have read many books on sandhyavandanam but couldn't get it.kindly suggest book title; name of author and publication and where to buy it. with kind regards. dr.omkara sreekrishna prayaga