This resource is part of a larger series supporting Algebraic Thinking across grade levels. I wanted to draw your attention to two parts of the series in particular relating to elementary learners - the K-2 and 3-5 editions.
Although a little older, Marilyn Burns resources are highly regarded, because they offer a balance of content area and pedagogical knowledge.
This resource is easily available online on
Amazon.com and
bookdepository.com. A significant portion of the books are available online in Google Books. That way if you find what you see of interest, you can order the book.
But why use it? How is it helpful?