Proofwiki.org is mentioned as a resource, but the main focus is on recommending books for studying Ordinary Differential Equations. "Ordinary Differential Equations" by Ross is highlighted as a simple, informative, and enjoyable read that covers most topics from the third section and some from the fourth section of a typical curriculum. However, the exercises in Ross are considered too easy, prompting the suggestion to also use "Ordinary Differential Equations" by Zill for more challenging exercises. For comprehensive coverage of the fourth section, a second book on Differential Equations is advised, although no specific recommendation is provided. The book by Arnold is noted as advanced but readable.