Who you cite is your business and nobody else's. You don't need to ask permission to cite  (unless you're reproducing images or something), and nobody can deny you the right to cite them, for whatever reason.

More importantly, if your work draws from someone's work, you must cite them, it's imperative. No personal equations can change that.

Who you cite is your business and nobody else's. You don't need to ask permission to cite(unless you're reproducing images or something*), and nobody can deny you the right to cite them, for whatever reason.

More importantly, if your work draws from someone's work, you must cite them, it's imperative. No personal equations can change that.

*In this case too, as pointed out by corey979, the permission is for copyright rather than citation, and the parties involved could include the publisher.