Shiva Purana
सूक्ष्मप्रणवरूपं हि सूक्ष्मरूपं तु निष्फलम् । स्थूललिंगं हि सकलं तत्पंचाक्षरमुच्यते २८ ।
It is called Sūkṣma Praṇava (the subtle one) if it is Niṣkala. The Sthūla (gross one) is Sakala and it consists of five constituent syllables.
english translation
sUkSmapraNavarUpaM hi sUkSmarUpaM tu niSphalam । sthUlaliMgaM hi sakalaM tatpaMcAkSaramucyate 28 ।
hk transliteration by Sanscript