Shiva Purana
सर्वेष्वपि च मासेषु पक्षयोरुभयोरपि ॥ अष्टाभ्यां च चतुर्दश्यां तथा पर्वाणि च क्रमात् ॥ २ ॥
In all the months, in both the fortnights and the fortnights, The eighth and fourteenth days of the month are also celebrated in this order.
english translation
sarveSvapi ca mAseSu pakSayorubhayorapi ॥ aSTAbhyAM ca caturdazyAM tathA parvANi ca kramAt ॥ 2 ॥
hk transliteration by Sanscript