Information about the author (P.D. Magnus, professor at the University at Albany, State University of New York) of the book "forallx An Introduction to Formal Logic", available below, is provided here. 

"His primary research is in the philosophy of science, motivated by a fallibilist but non-skeptical conception of scientific knowledge. He has published on under-determination, scientific realism, and natural kinds; also on related issues in the history of philosophy, social epistemology, and art ontology. He is the author of Scientific Enquiry and Natural Kinds: From Planets to Mallards (2012) as well as dozens of articles."

                (excerpt from the faculty profile of Department of Philosophy, University of Albany)

     forallx An Introduction to Formal Logic