Fix link

Fix broken link.

Author: Amanda Butler

docs/reference/contributing/connectivity/CellularInterface.md

@@ -182,7 +182,7 @@ Only valid when **Case 4** is applicable.
 
 Only valid when **Case 1** is applicable.
 
-* This is the most complex case - the bulk of the work is implementing the [NSAPI socket and network interfaces](/docs/v5.6/reference/api-references.html#network-sockets). The driver implementation derives from `CellularBase` to provide both the `NetworkInterface API` and the standard cellular API. Further layering to abstract connection type may be appropriate, as for the PPP case.
+* This is the most complex case - the bulk of the work is implementing the [NSAPI socket and network interfaces](/docs/v5.6/reference/network-socket-overview.html). The driver implementation derives from `CellularBase` to provide both the `NetworkInterface API` and the standard cellular API. Further layering to abstract connection type may be appropriate, as for the PPP case.
 
 * Use a file handle, such as `UARTSerial`, to provide the raw data connection; then you can use `ATCmdParser` to handle connection logic and the data flow of the socket API, assuming that you use AT commands to control the sockets.