The statement that utilitarianism permits sacrificing one individual to save the lives of many reflects the core foundational principle of act utilitarianism, which seeks to maximize overall well-being and aggregate outcomes.
The claim defines a foundational tenet of utilitarian ethical theory (maximizing aggregate welfare, often contrasted with deontology in scenarios like the trolley problem). While several papers discuss utilitarian cost-benefit reasoning or moral dilemmas, the definition of an ethical framework's core normative rule is a matter of philosophical definition rather than an empirical hypothesis requiring a citation receipt.