  We consider a multi-agent resource allocation setting in which an agent's
utility may decrease or increase when an item is allocated. We take the group
envy-freeness concept that is well-established in the literature and present
stronger and relaxed versions that are especially suitable for the allocation
of indivisible items. Of particular interest is a concept called group
envy-freeness up to one item (GEF1). We then present a clear taxonomy of the
fairness concepts. We study which fairness concepts guarantee the existence of
a fair allocation under which preference domain. For two natural classes of
additive utilities, we design polynomial-time algorithms to compute a GEF1
allocation. We also prove that checking whether a given allocation satisfies
GEF1 is coNP-complete when there are either only goods, only chores or both.
