@article{CM_1975__30_3_259_0,
     author = {Carroll, Joseph E.},
     title = {On determining the quadratic subfields of $Z_2$-extensions of complex quadratic fields},
     journal = {Compositio Mathematica},
     pages = {259--271},
     publisher = {Noordhoff International Publishing},
     volume = {30},
     number = {3},
     year = {1975},
     mrnumber = {374082},
     zbl = {0314.12005},
     language = {en},
     url = {http://archive.numdam.org/item/CM_1975__30_3_259_0/}
}