A set of chapters from the interactive text Active Calculus, focusing on Multivariable functions. Hosted online at https://activecalculus.org/multi/book-1.html.
A selection of readings assembled for Noba by Julie Reese. Available online at https://nobaproject.com/textbooks/new-textbook-6af59ac0-4729-47d4-af57-f2e591379bb6.