Preferred source of information:
Title page
If no title page: use information from cover, colophon pages, or anywhere within the resource.

Other source of information:

Accompanying materials, etc. or any other available source.

If information outside of the resource is used in certain elements, indicate this by placing the information in brackets. These elements include:

• title proper
• parallel title proper
• other title information
• all the subelements under statements of responsibility:
  • edition statement
  • production statement
  • publication statement
  • distribution statement
  • manufacture statement
  • series statement

Putting data from sources outside your resource in brackets is enough. Notes on where you get the information are unnecessary.