Arthashastra
शम अन्तरं पत्तिं स्थापयेत् त्रि शम अन्तरम् अश्वम्, पञ्च शम अन्तरं रथं हस्तिनं वा ॥
The infantry should be arrayed such that the space between any two men is a sama (14 angulas); cavalry with three samas; chariots with four samas; and elephants with twice or thrice as much space (as between any two chariots).
english translation
zama antaraM pattiM sthApayet tri zama antaram azvam, paJca zama antaraM rathaM hastinaM vA ॥
hk transliteration by Sanscript