▁must ▁have ▁a ▁gu ar ant or ▁of ▁unity . ▁This ▁gu ar ant or ▁cannot ▁be ▁other ▁than ▁a ▁component ▁of ▁the ▁representation , ▁hence ▁a ▁legal ▁proposition . ▁Being ▁a ▁legal ▁proposition , ▁it ▁counts ▁as ▁a ▁representation ▁of ▁an ▁actual ▁norm . ▁So ▁K elsen ▁calls ▁it , ▁elli pt ically , ▁a ▁' basic ▁norm ▁( G rund norm ) '. ▁ ▁Notes ▁ ▁S ources ▁ ▁Further ▁reading ▁ ▁Selected ▁works ▁by ▁K elsen ▁Re ine ▁Rechts le hre , ▁Vienna ▁ 1 9 3 4 . ▁Introduction ▁to ▁the ▁Problem s ▁of ▁Leg al ▁Theory ▁( 1 9 3 4 ; ▁L itsch ew ski ▁Paul son ▁and ▁Paul son ▁trans .), ▁Oxford ▁ 1 9 9 2 ; ▁the ▁transl ators ▁have ▁adopted ▁the ▁sub title ▁of ▁the ▁first ▁edition , ▁Ein leitung ▁in ▁die ▁re chts wissenschaft liche ▁Problem at ik , ▁in ▁order ▁to ▁avoid ▁confusion ▁with ▁the ▁English ▁translation ▁of ▁the ▁second ▁edition . ▁' On ▁the ▁Theory ▁of ▁Inter pret ation ' ▁( 1 9 3 4 ; ▁L itsch ew ski ▁Paul son ▁and ▁Paul son ▁trans .) ▁( 1 9 9 0 ) ▁ 1 0 ▁Leg al ▁Studies ▁ 1 2 7 . ▁Law ▁and ▁Peace ▁in ▁International ▁Rel ations , ▁Cambridge ▁( M ass .) ▁ 1 9 4 2 , ▁Union ▁( N . J .) ▁ 1 9 9 7 . ▁Peace ▁Through ▁Law , ▁Chap el ▁Hill ▁ 1 9 4 4 , ▁Union ▁(