The claim that a time-varying electric field generates a magnetic field is a fundamental axiom of classical electrodynamics, described by Maxwell-Ampere's law, and does not require citation.
The claim represents a foundational law of physics (Maxwell's extension of Ampere's law, where a displacement current or time-varying electric field produces a magnetic field). By instructions, a statement that is trivially true by definition or established physical law is classified as common knowledge, and no citations are needed.