@article{BUMI_2006_8_9B_1_a10,
     author = {Mencherini, Lorenzo},
     title = { A simple necessary and sufficient condition for well-posedness of $2 \times 2$ differential systems with time-dependent coefficients},
     journal = {Bollettino della Unione matematica italiana},
     pages = {215--220},
     publisher = {mathdoc},
     volume = {Ser. 8, 9B},
     number = {1},
     year = {2006},
     zbl = {1150.35065},
     mrnumber = {2204908},
     language = {it},
     url = {https://geodesic-test.mathdoc.fr/item/BUMI_2006_8_9B_1_a10/}
}