Construction of class fields over imaginary biquadratic fields Ja Kyung KooDong Sung Yoon Indiana University Mathematics Journal 2019 text pdf 10.1512/iumj.2019.68.7626 10.1512/iumj.2019.68.7626 en Indiana Univ. Math. J. 68 (2019) 413 - 434 state-of-the-art mathematics http://iumj.org/access/