Brihat Parashara Hora Shastra
अष्ट्मोंऽशो निरीशः स्याच्छन्यंशो गुलिकःस्मृतः। रात्रिमप्यष्टधा कृत्वा वारेशात् पञ्चमादितः॥ ६७॥
Whichever portion is ruled by Śani, will be the portion of Gulik. Similarly make the night duration into eight equal parts and distribute these, commencing from the Lord of the 5th (by) week.
english translation
aSTmoM'zo nirIzaH syAcchanyaMzo gulikaHsmRtaH। rAtrimapyaSTadhA kRtvA vArezAt paJcamAditaH॥ 67॥
hk transliteration by Sanscript