The biography uses mostly 'secondary' sources. [=information that did not come from original/primary sources but came from research done by others]
There are some 'secondary' issues/considerations which must be taken into account as well.
In some children's books, the text is 'secondary to' the illustrations.
(..) Again. If you want to hit this thing, it's gonna be complicated. Your scan doesn't show the internal structure. There's an outer row of columns. Real heavy duty. There's a secondary ring here, and an inner ring. There's a core structure like a spiral. That's how they move up and down. Roger that. What else can you tell us about the structure? I'm guessing this secondary ring, that's also load-bearing. - So where are we going? - Getting out of Dodge. I'm not about to let Selfridge and Quaritch micro-manage this thing. There's a mobile link up at Site we can work out of, (..)2009 Avatar