Arthashastra
पत्त्य् अश्व रथ द्विपानां सार त्रि भागम् उरस्यं स्थापयेत्, द्वौ त्रि भागौ कक्षं पक्षं च उभयतः, अनुलोमम् अनुसारम्, प्रतिलोमं तृतीय सारम्, फल्गु प्रतिलोमम् ॥
One-third of the best of infantry, cavalry and elephants should be kept in front; two-thirds on both the flanks and wings; the array of the army according to the strength of its constituents is in the direct order; that which is arrayed mixing one-third of strong and weak troops is in the reverse order.
english translation
patty azva ratha dvipAnAM sAra tri bhAgam urasyaM sthApayet, dvau tri bhAgau kakSaM pakSaM ca ubhayataH, anulomam anusAram, pratilomaM tRtIya sAram, phalgu pratilomam ॥
hk transliteration by Sanscript