The subject matter of this specification can be embodied in, among other things, a method that includes identifying resources relating to an entity, where each resource includes multiple terms and is included in a corpus of resources relating to multiple entities. The PLL circuit includes a phase detection circuit and a frequency detection circuit. In response to an authentication request, the client application can select a token and split it into multiple parts. When the refrigerant flows in from the first joint pipe and flows out from the second joint pipe, the first and second expansion valves are in semi-closed state. Thus, the next time period allocated by the SCP for the call can be billed at a rate that reflects the mobile subscriber’s location at that time as reported by the MSC or GMSC. The SPE is low cost and user friendly.