Shiva Purana
पूर्वं कृतयुगं नाम ततस्त्रेता विधीयते ॥ द्वापरं च कलिश्चैव युगान्येतानि कृत्स्नशः ॥ १२ ॥
The first Yuga is Kṛta, then comes Tretā. Dvāpara and Kali are the other Yugas. These are the four Yugas.
english translation
pUrvaM kRtayugaM nAma tatastretA vidhIyate ॥ dvAparaM ca kalizcaiva yugAnyetAni kRtsnazaH ॥ 12 ॥
hk transliteration by Sanscript