Arthashastra
विशिष्टानां च एक पात्रं विवाहं वा हीनेभ्यो वारयेयुः ॥
they may prevent the superiors from interdining and intermarriage with others.
english translation
viziSTAnAM ca eka pAtraM vivAhaM vA hInebhyo vArayeyuH ॥
hk transliteration by Sanscript