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.
(..) excited about the opportunities that affords. If we go remote, we can lose the control panels, the secondary and tertiary comm systems. He's not even got to the bad stuff yet, Vincent. Let's skip to the bad stuff! (..)2015 The Martian