Alan Libert has published several books in the field of interlinguistics and related topics, among them:
Libert, Alan. A Priori Artificial Languages. Muenchen: Lincom Europa, 2000.
Libert, Alan. Artificial Descendants of Latin. München: Lincom Europa, 2004.
Libert, Alan Reed. Daughters of Esperanto. München: Lincom Europa, 2008.
Libert, Alan. Mixed Artificial Languages. München: Lincom Europa, 2003.
Moskovsky, Christo; Libert, Alan. Essays on Natural and Artificial Languages. Frankfurt/Main: Peter Lang, 2009.
Libert, Alan Reed. "What can Pragmaticists Learn from Studying Artificial Languages?," in Perspectives on Linguistic Pragmatics, edited by Alessandro Capone, Franco Lo Piparo, Marco Carapezza (New York : Springer, 2013), pp. 397-432.
See also articles in Journal of Universal Language, under the auspices of Language and Translation Research Institute, Sejong University, Korea (See also listing of individual articles on my site)
"Questions in Natural and Artificial Languages" by Christo Moskovsky & Alan Libert. Volume 7 Number 2, 2006, pp. 65-120And here is a video of Libert speaking on the a priori language project Fitusa / Jen video de Alan Libert pri apioria lingvoprojekto Fitusa:
"Possibilities for Passives in Natural and Artificial Languages" by Christo Moskovsky & Alan Libert. Volume 5 Number 2, 2004, pp. 101-149
"A Survey of Relative Pronouns and their Uses in Natural and Artificial Languages" by Alan Libert & Christo Moskovsky. Volume 4 Number 2, 2003, pp. 61-116