This site lists six specific sources in its own "Research References" section — worth reading this collection together, through the exact framing this site itself applies to them.
This site is direct: background reading on the two ingredients Golden Brain names — these concern the individual ingredients, not a clinical trial of the finished product.
Two NCCIH overviews (Lion's Mane, Bacopa), two PubMed search links (Bacopa and memory, Hericium and cognitive function), one NIA resource on memory and aging, and one FDA page on dietary supplements generally.