Brihat Samhita
यावन्त्यहानि दृश्यो मासास्तावन्त एव फलपाकः । मासैरब्दांश्च वदेत्प्रथमात्पक्षत्रयात्परतः ॥ ११-०७ ॥
The effects will last for as many months as the number of days during which the Ketus continue to be visible; if visible for months, the effects will last for years. The effects will commence after three weeks from such appearances.
english translation
yAvantyahAni dRzyo mAsAstAvanta eva phalapAkaH । mAsairabdAMzca vadetprathamAtpakSatrayAtparataH ॥ 11-07 ॥
hk transliteration by Sanscript