Christoph Stasch Krzysztof Janowicz Arne Bröring Ilka Reis Werner Kuhn A Stimulus-Centric Algebraic Approach to Sensors and Observations. 169-179 2009 GSN http://dx.doi.org/10.1007/978-3-642-02903-5_17 conf/gsn/2009 db/conf/gsn/gsn2009.html#StaschJBRK09