4 targets to act trigger

[stephen271276]

Lets say i have 4 targets boss1,boss2, boss3 and boss4......

What would i put in the condition of a trigger to activate it only when all four are not alive?

[celoush]

(!alive boss1) and (!alive boss2) and (!alive boss3) and (!alive boss4)  

try http://en.wikipedia.org/wiki/Propositional_calculus