Shiva Purana
तृतीयावरणे भेदो विद्यते स तु कथ्यते ॥ चतस्रो मूर्तयस्तस्य पूज्याः पूर्वादितः क्रमात् ॥ ५२ ॥
There is a difference in the third covering, which is called the covering. The four idols of him are to be worshiped in order from the east.
english translation
tRtIyAvaraNe bhedo vidyate sa tu kathyate ॥ catasro mUrtayastasya pUjyAH pUrvAditaH kramAt ॥ 52 ॥
hk transliteration by Sanscript