Extension of $b_f$-continuous functions defined on a product of $b_f$-groups

[EN] Let X be a bf -space and let G be a bf -group. By means of the exponential mapping we characterize when a bf -continuous function on X × G with values in a topologically complete sapce Z has a bf -continuous extension to β(X) × G. As a consequence we show that the product of a pseudocompact space and a bf -group is a bf -group. This result generalizes the fact that the product of a pseudocompact space and a pseudocompact group is pseudocompact.