Heat transfer from the Earth's core through the mantle via convection is a well-established foundational concept in geophysics and does not require citation.
The claim that heat is transferred from the Earth's core through the mantle primarily by convection is a fundamental scientific fact taught in introductory geology and geophysics. It is common knowledge within the scope of Earth sciences, well-supported by basic physical principles of fluid dynamics and thermal transport inside planets, rendering specific citations unnecessary.