The book is based mainly on 'primary' sources rather than secondary sources.
a new 'primary school' [=('US') 'elementary school', ('US') 'grade school']
The 'primary' function of our schools is to educate our young people.
(..) It's a Soviet-era anti-tank mine. There are still thousands of them in Afghanistan. Jihadist terror groups have been using them for years as their primary IEDs. Hannah, you hearing this? Agent Wells, the bomb is... Is an unexploded munition you think was used by a Mideast terror group... (..)2016 TvShow: Designated Survivor Title: Pilot Season: 1 Episode 1