Shiva Purana
नमःसेनेति मंत्रेण महामुद्रा ं! प्रदर्शयेत् । दर्शयेद्धेनुमुद्रा ं! च नमो गोभ्य ऋचानया ३५ ।
The Mahāmudrā shall be shown with the mantra “Namaḥ Senā-”॥ 50॥ etc. He shall then show the Dhenumudrā with the mantra “Namo Gobhyaḥ”. etc.
english translation
namaHseneti maMtreNa mahAmudrA M! pradarzayet । darzayeddhenumudrA M! ca namo gobhya RcAnayA 35 ।
hk transliteration by Sanscript