The Heisenberg uncertainty principle fundamentally establishes a lower bound on the product of standard deviations of incompatible observables, such as position and momentum. No citation is needed for this well-established physical definition.
The claim defines a core foundational tenet of quantum mechanics (the Heisenberg uncertainty principle as formalized by Robertson and others, establishing the lower bound on the product of standard deviations). This is a textbook definition and a matter of standard physical consensus, falling squarely under common knowledge where formal literature citations are unnecessary for verification.