Theory of marbles was probably "invented" (or its relation to larpdesign discovered) in Norway.
Erlend Eidsem Hansen published an article about larp dramaturgy dividing plotstructures into 3 main strategies : railroading, branching and marbles in his underground larpfanzine "Guru" in 1993.
Also some (old) texts on larphacking are gathered at: [http://scratchpad.wikia.com/wiki/Category:LarpHacking Larp Hacking Wiki] (the wiki is referring to a workshop at KP 2007 and a roundtable/panel-discussion in SK 2008).
== Notable usages of this technique ==