  The antenna subtraction formalism allows to calculate QCD corrections to jet
observables. Within this formalism, the subtraction terms are constructed using
antenna functions describing all unresolved radiation between a pair of hard
radiatior partons. In this paper, we focus on the subtraction terms for double
real radiation contributions to jet observables in hadron-hadron collisions
evaluated at NNLO. An essential ingredient to these subtraction terms are the
four-parton antenna functions with both radiators in the initial state. We
outline the construction of the double real subtraction terms, classify all
relevant antenna functions and describe their integration over the relevant
antenna phase space. For the initial-initial antenna functions with two quark
flavours, we derive the phase space master integrals and obtain the integrated
antennae.
