@article{10_4153_S0008439520000855,
     author = {Chen, Yin},
     title = {Relations between modular invariants of a vector and a covector in dimension two},
     journal = {Canadian mathematical bulletin},
     pages = {820--827},
     year = {2021},
     volume = {64},
     number = {4},
     doi = {10.4153/S0008439520000855},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/S0008439520000855/}
}