Surya Siddhanta
बवादीनि ततः सप्त चराख्यकरणानि च। मासे +अष्टकृत्व एकैकम् करणानाम् प्रवर्तते ॥
And the seven variable Karaṇas, Bava[1] &c. afterwards succeed each other regularly, through eight repetitions in a (lunar) month.
english translation
bavAdIni tataH sapta carAkhyakaraNAni ca। mAse +aSTakRtva ekaikam karaNAnAm pravartate ॥
hk transliteration by Sanscript