Helfert, E. A. (1967). Techniques of financial analysis (Rev. ed.). R.D. Irwin.

Helfert, Erich A. Techniques of Financial Analysis. Rev. ed. Homewood, Ill.: R.D. Irwin, 1967.

Helfert, Erich A. Techniques of Financial Analysis. Rev. ed. R.D. Irwin, 1967.