@article {Pljakov1989, title = {La r{\'e}gion de la Moyenne Struma aux VIIe{\textendash}IXe si{\`e}cles}, journal = {Palaeobulgarica / Старобългаристика}, volume = {13}, year = {1989}, pages = {100{\textendash}115}, author = {Pljakov, Zdravko} }