The paper by Krause, Schafer, and Kulander explores high-order harmonic generation (OHG) from atoms and ions under high-intensity laser conditions, relevant to current short-pulse experiments. They find that ions can produce harmonics comparable in strength to those from neutrals, extending to much higher orders. The authors suggest simple scaling laws for the strength of harmonic emission and the maximum observable harmonic, based on the wavelength of the driving field, the saturation intensity, and the ionization potential (I_p) of the species. These results imply that recent experiments in helium and neon may have observed contributions from both neutrals and ions. The study uses numerical methods to solve the time-dependent Schrödinger equation for one-electron systems and the time-dependent Hartree-Fock equations for multi-electron systems. The authors present a formula to estimate the maximum observable harmonic and discuss the scaling relations and phase-matching conditions affecting harmonic emission. They conclude that while most experimental data can be explained by neutral emission, recent experiments in helium and neon suggest significant contributions from ions.The paper by Krause, Schafer, and Kulander explores high-order harmonic generation (OHG) from atoms and ions under high-intensity laser conditions, relevant to current short-pulse experiments. They find that ions can produce harmonics comparable in strength to those from neutrals, extending to much higher orders. The authors suggest simple scaling laws for the strength of harmonic emission and the maximum observable harmonic, based on the wavelength of the driving field, the saturation intensity, and the ionization potential (I_p) of the species. These results imply that recent experiments in helium and neon may have observed contributions from both neutrals and ions. The study uses numerical methods to solve the time-dependent Schrödinger equation for one-electron systems and the time-dependent Hartree-Fock equations for multi-electron systems. The authors present a formula to estimate the maximum observable harmonic and discuss the scaling relations and phase-matching conditions affecting harmonic emission. They conclude that while most experimental data can be explained by neutral emission, recent experiments in helium and neon suggest significant contributions from ions.