Zeros of ${\mathrm{G}\mathrm{L}}_2$ $L$-functions on the critical line

We use Levinson’s method and the work of Blomer and Harcos on the ${\mathrm{G}\mathrm{L}}_2$ shifted convolution problem to prove that at least 6.96% of the zeros of the L-function of any holomorphic or Maass cusp form lie on the critical line.