Resources for images

[wadid]

Hi Oleh, very nice Spring notes! Especially the pictures. Much better to visualize the relationships than to write a lot of text.

I wanted to ask where some of the images came from?
e.g. https://github.com/linnykoleh/Spring/blob/master/images/handout/Screenshot_15.png or the also the "spring in details" image files? Is there a book out there or did you make them yourself?