TY - JOUR T1 - Searches for Gravitational Waves from Known Pulsars at Two Harmonics in the Second and Third LIGO-Virgo Observing Runs PY - 2021/11/25 AU - The LIGO Scientific Collaboration AU - the Virgo Collaboration AU - the KAGRA Collaboration AU - Abbott R AU - Abe H AU - Acernese F AU - Ackley K AU - Adhikari N AU - Adhikari RX AU - Adkins VK AU - Adya VB et al ED - DO - DOI: 10.48550/arxiv.2111.13106 Y2 - 2025/10/08 ER -