Denver. Business. Investments Penny stock market: boom and opponents. RM F 3, 1981 p.8B-9B,10B District attorney warns of Penny stock market pitfalls. RM F 20, 1981 p. 6 Penny stocks performing well, says J. Daniel Bell and Co., broker who specializes. RM F 6, 1981 p. 69 Charges expected in DA's OTC probe; DA agrees to meet with stock brokers. rocky mountain RM Journal Ap 22, 1981 p.1 Penny stocks business in Denver declines. RMNO Ap 26, 1981 p.lB,6B