I wanted to share this web page by Umami Information Center. It is accredited by Japanese Govt and their purpose is to spread the accurate information about what consitutes umami.
Generally umami rich foods have synergistic effect of glutamate and iosinate or glutamate and guanylate. It is through combining these properties which increase the umami in recipes. They list food items with their properties. What I find interesting is I see some claims of canned/bottled anchovies or fish sauce having inosinate properties, but according to this org, iosinates in fish are broken down to glutamates during their processing and no iosinates remain. Same for other fish/seafood sauces such as oyster sauce.
I find their info very interesting. www.umamiinfo.com/richfood/