The dry adiabatic lapse rate is a well-established physical constant in meteorology representing the rate of temperature decrease with altitude for an unsaturated parcel of air, and thus no citation is needed.
The claim states the standard dry adiabatic lapse rate, which is approximately 9.8 degrees Celsius per kilometer (or about 9.8 K/km). This is a fundamental physical constant defined by gravity and the specific heat capacity of dry air, making it a matter of common knowledge and textbook physics rather than a hypothesis requiring empirical debate in the provided literature.