Arthashastra
अरि विजिगीषु मध्यानां बहिः प्रकृतिभ्यो बलवत्तरः संहत असंहतानाम् अरि विजिगीषु मध्यमानाम् अनुग्रह समर्थो निग्रहे च असंहतानाम् उदासीनः ॥
The conqueror, his friend, and his friend's friend are the three primary kings constituting a circle of states. As each of these three kings possesses the five elements of sovereignty, such as the minister, the country, the fort, the treasury, and the army, a circle of states consists of eighteen elements. Thus, it needs no commentary to understand that the (three) Circles of States having the enemy (of the conqueror), the Madhyama king, or the neutral king at the centre of each of the three circles, are different from that of the conqueror.
english translation
ari vijigISu madhyAnAM bahiH prakRtibhyo balavattaraH saMhata asaMhatAnAm ari vijigISu madhyamAnAm anugraha samartho nigrahe ca asaMhatAnAm udAsInaH ॥
hk transliteration by Sanscriptअरि विजिगीषु मध्यानां बहिः प्रकृतिभ्यो बलवत्तरः संहत असंहतानाम् अरि विजिगीषु मध्यमानाम् अनुग्रह समर्थो निग्रहे च असंहतानाम् उदासीनः ॥
The conqueror, his friend, and his friend's friend are the three primary kings constituting a circle of states. As each of these three kings possesses the five elements of sovereignty, such as the minister, the country, the fort, the treasury, and the army, a circle of states consists of eighteen elements. Thus, it needs no commentary to understand that the (three) Circles of States having the enemy (of the conqueror), the Madhyama king, or the neutral king at the centre of each of the three circles, are different from that of the conqueror.
english translation
ari vijigISu madhyAnAM bahiH prakRtibhyo balavattaraH saMhata asaMhatAnAm ari vijigISu madhyamAnAm anugraha samartho nigrahe ca asaMhatAnAm udAsInaH ॥
hk transliteration by Sanscript