Some stations have the capability to interrupt the network through the local insertion of television commercials, station identifications and emergency alerts. Others completely break away from the network for their own programming, a method known as regional variation. This is common where small networks are members of larger networks. The majority of commercial television stations are self-owned, even though a variety of these instances are the property of an owned-and-operated television network. The commercial television stations can also be linked with a noncommercial educational broadcasting agency. It is also important to note that some countries have launched national television networks, so that individual television stations can act as common repeaters of nationwide programs.