: Many logic guides cover methods for constructing logical proofs, including natural deduction, sequent calculus, and truth tables. These are methods for systematically demonstrating the validity of arguments.
Before hunting for the PDF, one must understand the author. Gajo Petrović (1927–1993) was a Croatian Marxist philosopher and a leading member of the , a Yugoslav philosophical movement that sought to rethink Marx through the lenses of phenomenology, existentialism, and critical theory. Gajo Petrovic Logika.pdf
The specific PDF search likely refers to the 1979 edition (or thereabouts) published by and Liber . It is notoriously hard to find because it was largely out of print before the digitization boom of the 2000s, and much of the ex-Yugoslav academic archive remains un-scanned due to copyright and linguistic barriers. : Many logic guides cover methods for constructing