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This paper addresses the critical problem of interference management in two-tier networks, where the newly-deployed femtocell users (FUEs) operate in the licensed spectrum owned by the existing macrocell. A Pareto-optimal power-control algorithm is devised that jointly maximizes the utilities of both macrocell and femtocell networks while robustly guaranteeing the macrocell's quality-of-service (QoS) requirements. After effectively enforcing the minimum signal-to-interference-plus-noise ratios (SINRs) prescribed by the macrocell users (MUEs) with the use of a penalty function, the Pareto- optimal boundary of the strongly-coupling SINR feasible region is characterized. Based upon the specific network utility functions and also the target SINRs of the MUEs, a unique operating SINR point is determined, and transmit power adapted to achieve such a design objective. We prove that the developed algorithm converges to the global optimum, and more importantly, it can be distributively implemented at individual links. Effective mechanisms are also available to flexibly designate the access priority between macrocells and femtocells, as well as to fairly share the system resources among different users. The merits of the proposed approach are verified by numerical examples.