Brihat Parashara Hora Shastra
राशित्रिभागाद्रेष्काणास्ते च षट्त्रिंशदीरिताः। परिवृत्तित्रयं तेषां मेषादेः क्रमशो भवेत्॥ ७॥
counted from Mesh and repeated twice (at the rate of 12) in the whole of the zodiac. Dreshkan. One third of a Rāśi is called Dreshkan. These are totally 36, counted from Mesh, repeating thrice at the rate of 12 per round.
english translation
rAzitribhAgAdreSkANAste ca SaTtriMzadIritAH। parivRttitrayaM teSAM meSAdeH kramazo bhavet॥ 7॥
hk transliteration by Sanscript