@misc{Tesar-Skala-1989, 
    title={Patent: Device for indicating the difference between the desired and actual phase shift 
    (in {Czech}:  Zarizeni pro indikaci rozdilu zadaneho a skutecneho fazoveho posuvu)}, 
    author={Tesar, Rudolf and Skala, Vaclav}, 
    year={1989}, 
    month={April},
    country = {Czech Rep.},
    URL = {http://afrodita.zcu.cz/~skala/PUBL/PUBL\_1989/1989-patent-251399.pdf},
    note = {{Czech Rep.} Patent No.251399},
}