Philosophical Foundations of Physics
- Chapters 23 through 26 of this 1966 work.
- http://www.marxists.org/reference/subject/philosophy/works/ge/carnap.htm

Logical Foundations of Probability
- Excerpt from the 1950 paper by Carnap.
- http://www.lawrence.edu/fac/boardmaw/Carnap_Explica2.html

Empiricism, Semantics, and Ontology
- Paper by Rudolf Carnap, first published in Revue Internationale de Philosophie 4 (1950): 20-40.
- http://www.ditext.com/carnap/carnap.html