Brihat Samhita
व्यालं त्रयोदशऋक्षाच्चतुर्दशाद्वा विपच्यते अस्तमये । दंष्ट्रिव्यालमृगेभ्यः करोति पीडां सुभिक्षं च ॥ ६-०३ ॥
If he should begin to retrograde from the 13th or 14th constellation from that of his reappearance, such retrograde motion is known as vyāla: when he should disappear before his next conjunction with the Sun, wild boars and fierce animals will be afflicted with distress.
english translation
vyAlaM trayodazaRkSAccaturdazAdvA vipacyate astamaye । daMSTrivyAlamRgebhyaH karoti pIDAM subhikSaM ca ॥ 6-03 ॥
hk transliteration by Sanscript