Brihat Parashara Hora Shastra
सूर्यस्याऽर्धास्तयः पूर्वं परस्तादूदयादपि । पञ्च पञ्च घटी सन्ध्या दशनाडी प्रकीर्तिता ॥ ४४॥
5 Ghatikas before the sight of the semi-disk of the setting Sūrya and 5 Ghatikas after that and 5 Ghatikas before and after the rising of Sūrya, that is 10 Ghatikas in the evening and 10 Ghatikas in the morning, respectively.
english translation
sUryasyA'rdhAstayaH pUrvaM parastAdUdayAdapi । paJca paJca ghaTI sandhyA dazanADI prakIrtitA ॥ 44॥
hk transliteration by Sanscript