Carnap, Rudolf (1962), Logical Foundations of Probability. 2nd ed. Chicago: University of Chicago Press. Par. 87 (pp. 468-478). pdf

Further Readings:

Carnap, Rudolf (1945), The Two Concepts of Probability. Philosophy and Phenomenological Research 5, 513-532. pdf

Carnap, Rudolf (1947), On the Application of Inductive Logic. Philosophy and Phenomenological Research 8, 133-148. pdf

Carnap, Rudolf (1948), Reply to Nelson Goodman. Philosophy and Phenomenological Research 8, 461-462. pdf

Carnap, Rudolf (1963), Probability and Inductive Logic. In P.A. Schilpp (ed.), The Philosophy of Rudolf Carnap. La Salle, IL: Open Court, 71-77.

Carnap, Rudolf (1963), The Philosopher Replies: Probability and Induction. In P.A. Schilpp (ed.), The Philosophy of Rudolf Carnap. La Salle, IL: Open Court, 966-998.