The two-element linear concatenative basis
Brent Kerby calls out that ‘cons’ and ‘sap’ are a linear basis in a concatenative language.
The Theory of Concatenative Combinators » Linear Completeness
[B] [A] cons == [[B] A] [B] [A] sap == A B
This is a valid basis because ‘cons’ covers quoting and concatenation, and ‘sap’ covers reordering and unquoting.