1. Sang-Kil Son, “New opportunities in x-ray spectroscopy at high intensity” in XFEL Special Seminar (PAL XFEL, POSTECH, Pohang, Korea, July 20, 2023) [invited talk].
2. Sang-Kil Son, “Multiple-core-hole resonance spectroscopy with ultraintense X-ray pulses” in CFEL-DESY Theory Seminar (CFEL, DESY, Hamburg, Germany, September 20, 2023) [oral presentation].