Shiva Purana
अष्टमी सोमवारे च कृष्णपक्षे चतुर्दशी॥ शिवतुष्टिकरं चैतन्नात्र कार्या विचारणा॥ १९॥
Aṣṭamī that falls on Monday, and Caturdaśī in the dark half are sure to bring about the propitiation of Śiva.
english translation
aSTamI somavAre ca kRSNapakSe caturdazI॥ zivatuSTikaraM caitannAtra kAryA vicAraNA॥ 19॥
hk transliteration by Sanscript