Induism; Chapter 15 of Bhagavad Gita with reference to Upanishads.

Explain Chapter 15 of Bhagavad Gita with reference to Upanishads.
Please, be careful in selecting online sources and the right translation because some online information is not reliable. I am going to upload Chapter 15 from my book (The Beloved Lords Secret Love Song by Graham M.Schweig). From Upanishads we discussed in class Katha U., Mandukya U., Kena U., Prasna U., and Svetasvatara U. (Book: Upanisads by patrick Olivelle). You can include references and citations in the paper as long as ideas are right.
Please, do not hesitate to ask me any information. This work is very important for me, so I really rely on you.