Symbolic and mathematical.

100% mathematical proof Garnier, Rowan 1996 A concise introduction to pure mathematics Liebeck, Martin 2006 A conscise introduction to mathematical logic Rautenberg, Wolfgang 2006 A first course in mathematical logic and set theory O'Leary, Michael L. 2016 A mathematical introduction to logic Enderton, Herbert B. 2001 Advanced work in English Parker, Colin Rodwell Eric 1967 An essay in modal logic Wright, G. H. von 1951 An introduction to mathematical logic Robison, Gerson B. 1969 An Introduction to Modern Logic Halberstadt, William H. 1960 An introduction to practical formal methods using temporal logic Fisher, Michael 2011 An introduction to symbolic logic Langer, Susanne Katherina Knauth 1953 An introduction to the elements of mathematics Fujii, John N. 1961 Basic concepts of mathematics and logic Gemignani, Michael C. 1968 Basic concepts of mathematics and logic Gemignani, Michael C. 1968 Basic Discrete Mathematics Kohar, Richard 2016 Cancer risks and prevention Vessey, M.P. 1985 Classical and Fuzzy Concepts in Mathematical Logic and Applications Reghi?Mircea 1998 Cognitive reasoning Anshakov, oleg 2010 Completeness, compactness, and undecidability Manaster, Alfred B. 1975 Computability and logic Jeffrey, Richard C. 2002