If you absolutely need to cite individual surface datasets that are used in CLM, then I recommend looking here for citations:
Otherwise, simply citing the CLM5 overview paper and/or the technical note should be sufficient, e.g.,:
David M. Lawrence, Rosie A. Fisher, Charles D. Koven, Keith W. Oleson, Sean C. Swenson, Gordon Bonan, Nathan Collier, Bardan Ghimire, Leo van Kampenhout, Daniel Kennedy, Erik Kluzek, Peter J. Lawrence, Fang Li, Hongyi Li, Danica Lombardozzi, William J. Riley, William J. Sacks, Mingjie Shi, Mariana Vertenstein, William R. Wieder, Chonggang Xu, Ashehad A. Ali, Andrew M. Badger, Gautam Bisht, Michiel van den Broeke, Michael A. Brunke, Sean P. Burns, Jonathan Buzan, Martyn Clark, Anthony Craig, Kyla Dahlin, Beth Drewniak, Joshua B. Fisher, Mark Flanner, Andrew M. Fox, Pierre Gentine, Forrest Hoffman, Gretchen Keppel-Aleks, Ryan Knox, Sanjiv Kumar, Jan Lenaerts, L. Ruby Leung, William H. Lipscomb, Yaqiong Lu, Ashutosh Pandey, Jon D. Pelletier, Justin Perket, James T. Randerson, Daniel M. Ricciuto, Benjamin M. Sanderson, Andrew Slater, Zachary M. Subin, Jinyun Tang, R. Quinn Thomas, Maria Val Martin, Xubin Zeng, 2019: The Community Land Model version 5: Description of new features, benchmarking, and impact of forcing uncertainty.
Journal of Advances in Modeling Earth Systems, 11, 4245-4287.
https://doi-org.cuucar.idm.oclc.org/10.1029/2018MS001583.