I’m currently working on a small exhibit that should be shown in some zoos and other places to inform about a specific environmental issue and what people can do to conserve nature. It consists of a four-sided pillar with different subtopics, showpieces and a possibility to interact, like a microscope. Now I am searching for methods to evaluate if visitors take and understand the specific massage (“What can I do in that case?”). Do you know good literature for methods?  

Thank you a lot.