As an explanation of the title, the author writes:
Mark Twain once said that if the first thing you do each morning is to eat a live frog, you can go through the day with the satisfaction of knowing that that is probably the worst thing that is going to happen to you all day long.
I could not find the source for this quotation. It appears in various forms on motivational websites, in collections of quotes, etc., but never with any bibliographical details. Project Gutenberg’s collected works of Mark Twain include references to frogs, but nothing that I could see about eating them.
Credo Reference is a collection of online reference books. It can be browsed and searched like an encyclopedia.
For example, if you search for global warming, you are shown the topic page on climate change (“the now commonly used term, having replaced “global warming”), extracts from many books, a list of related topics (Climate change, Greenhouse gas, Kyoto Protocol, etc.), images, and a mind map.
It might be a good place to start research for your long essay or project.