springhead
ur-source
mother
straight from the horse's mouth
root
emanate
from good hands
at first hand
firsthand
last word
reference
trufax
authorship
give birth
title
have something on good authority
magisterium
founded
scripture
underpinning
wartweed
oroclinal
factualist
factically
fons et origo
factually
outpart
matter of fact
relevantly
font
thus
assertedly
dead-on
by
uredosporous
uredinous
uredosporic
uredineous
⠁⠉
strike
forenote
intersource
afore-explained
foundation stone
grass roots
basics
scholarly
bairn's part
rudiments
materially