The magnificent prelude that Sankara wrote to his commentary on the Vedanta Sutras is celebrated as The Adhyasa Bashya. It is in fact not a Bhashya; it is not a commentary. It is an independent piece of writing, which served as a prologue to his main work.
Part 2 - Learn Sanskrit
Part 1 - Learn Sanskrit
Talks on Advanced Vedanta by Acharya Sadaji
Taittiriya Upanishad by Prof Mahadevan B
Gita Study by Karnam Aravinda Rao