  A method is developed for analysing asymptotic behaviour of terms involving
an arbitrary integer order powers of L p functions by means of H-measures. It
is applied to the small amplitude homogenisation problem for a stationary
diffusion equation, in which coefficients are assumed to be analytic
perturbations of a constant, enabling formul{\ae} for higher order correction
terms in a general, non-periodic setting. Explicit expressions in terms of
Fourier coefficients are obtained under periodicity assumption. The method
enables its generalisation and application to the corresponding non-stationary
equation, as well as to some other small amplitude homogenisation problems.
