Arthashastra
कुर्याद् गव अश्व व्यायोगं रथेष्व् अल्प हयो नृपः । खर उष्ट्र शकटानां वा गर्भम् अल्प गजस् तथा ॥
The king who has a small number of horses may combine bulls with horses; likewise when he is deficient in elephants, he may fill up the centre of his army with mules, camels and carts.
english translation
kuryAd gava azva vyAyogaM ratheSv alpa hayo nRpaH । khara uSTra zakaTAnAM vA garbham alpa gajas tathA ॥
hk transliteration by Sanscript