The document discusses challenges, guidelines, techniques, and contact information related to cognitive radio networks (CRN). It lists six main challenges for CRN including security awareness of spectrum, coordination between secondary users, optimal channel assignment, seamless handover of spectrum, accuracy in sensed spectrum, and exchange of control messages. It also outlines variable directions for CRN research including energy harvesting, resource allocation, routing, spectrum sharing, detection, sensing, and dynamic spectrum access. Finally, it provides potential techniques for resource allocation and routing in CRN such as fault tolerant routing, spectrum stability aware routing, various game theories, and multi-objective optimization algorithms.