Singular cardinals and strong extenders
  We investigate the circumstances under which there exist a singular cardinal $\mu$ and a short $(\kappa, \mu)$-extender $E$ witnessing "$\kappa$ is $\mu$-strong", such that $\mu$ is singular in $\Ult(V, E)$. 
Arthur W. Apter, James Cummings, Joel David Hamkins
math.LO