Arthashastra
त्रीणि त्रिकाण्य् अनीकं रथानाम् उरस्यं स्थापयेत्, तावत् कक्षं पक्षं च उभयतः ॥
Three groups (aníka) of three chariots each should be stationed in front; the same number on the two flanks and the two wings.
english translation
trINi trikANy anIkaM rathAnAm urasyaM sthApayet, tAvat kakSaM pakSaM ca ubhayataH ॥
hk transliteration by Sanscript