Direct case

A

case which

the

and

other

such as

(the

system

; the

is used especially in

systems with two or three

)

A

for the

, based on the

by Peter Edmund Laurent [https://books.google.ca/books?id=66NWAAAAcAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q=direct&f=false [1]]