The collaboration of multiple Cloud Providers (CPs) with the intent to share resources with each other and enhance resource availability to customers is termed as Cloud Federation. The collaboration of participating CPs is based on mutual agreements among them with all the terms and conditions of association mentioned in the form of a Federation Level Agreement (FLA). A proper approach for pricing of resources is a pre-requisite in such an environment. This is mainly because genuine bills for users and lucrative revenue for CPs can be generated only when a suitable approach to price the resources is available. Thus, literature review is performed in this paper to identify an appropriate mechanism for impartial pricing of resources contributed by various CPs in a Federation of Clouds. The review provides information about the existing mechanisms of resource pricing, revenue sharing and their limitations. It is observed from the review that none of the pricing mechanisms proposed in the literature ensures fair bills for users and genuine revenue share for all the collaborating CPs. This calls for the requirement to propose appropriate mechanisms to charge users that can address the problems associated with current mechanisms.