Shiva Purana
प्रजाभिस्तपसा युक्ता ब्रह्मलोकं व्रजंति ते ॥ युगानि सप्रतिस्त्वेकं साग्राण्यंतरमुच्यते ॥ ७१ ॥
Endowed with austerities by the subjects they attain the world of Brahma One of the ages is called the interval between the peaks.
english translation
prajAbhistapasA yuktA brahmalokaM vrajaMti te ॥ yugAni sapratistvekaM sAgrANyaMtaramucyate ॥ 71 ॥
hk transliteration by Sanscript