Shiva Purana
अकारं मूर्ध्नि विन्यस्य आकारं च ललाटके ॥ इं ईं च नेत्रयोस्तद्वतुं ऊं श्रवणयोस्तथा ॥ २४ ॥
The syllable a is placed on the head and the syllable a is placed on the forehead. Iṁ īm is the same for the eyes, and oom is for the ears.
english translation
akAraM mUrdhni vinyasya AkAraM ca lalATake ॥ iM IM ca netrayostadvatuM UM zravaNayostathA ॥ 24 ॥
hk transliteration by Sanscript