@article{DeFreitas:2013I6, author = "De Freitas, Abilio and Bluemlein, Johannes and van Neerven, Wilhelmus", title = "{Two-Loop QED Operator Matrix Elements with a Massive External Fermion Line}", doi = "10.22323/1.145.0033", journal = "PoS", year = 2013, volume = "RADCOR2011", pages = "033" }