Shiva Purana
अविमुक्ते महाक्षेत्रे सिद्धक्षेत्रे हि तत्परम् ॥ यत्रास्ते परमं लिंगं मध्यमेश्वरसंज्ञकम् ॥ ७७ ॥
That is the ultimate in the unreleased great field of perfection There is the supreme Lingam called Madhyameshvara.
english translation
avimukte mahAkSetre siddhakSetre hi tatparam ॥ yatrAste paramaM liMgaM madhyamezvarasaMjJakam ॥ 77 ॥
hk transliteration by Sanscript