added XSD and WSDL link/reference

doc/general/communication/communication.md

@@ -43,6 +43,8 @@ Simple Object Access Protocol (SOAP) is a network protocol which can exchange da
 
 With [`<basicHttpBinding>`](https://msdn.microsoft.com/en-us/library/system.servicemodel.basichttpbinding\(v=vs.110\).aspx), [`<netNamedPipeBinding>`](https://msdn.microsoft.com/en-us/library/system.servicemodel.netnamedpipebinding\(v=vs.110\).aspx) and [`<netTcpBinding>`](https://msdn.microsoft.com/en-us/library/system.servicemodel.nettcpbinding\(v=vs.110\).aspx), fiskaltrust.Service makes its functionality available on the local network.
 
+A WSDL file which describes the fiskaltrust.service is available at [dist/WSDL](https://github.com/fiskaltrust/interface-doc/tree/master/dist/WSDL).
+
 **C# call for signing with SOAP:**
 ```cs
 //create proxy and establish authentification
@@ -66,6 +68,8 @@ Representational State Transfer architecture uses the classic http methods GET,
 
 The functions accept POST requests and use the endpoint set via the parameter "host" as basis. The URL is extended by `/[xml | json]/[echo | sign | journal]` in order to call the respective functions.
 
+XSD files are available which describes the fiskaltrust.service at [dist/XSD](https://github.com/fiskaltrust/interface-doc/tree/master/dist/XSD).
+
 #### *Balancer Helper*
 
 The Balancer helper uses the standard calls from .net WCF WebInvoke for the implementation of REST. There are a few particular characteristics, stemming from the REST specification, e.g.: the dates have to be indicated in "wire format", details about these conventions can be found at: