AMGen 1900 Oak Terrace Lane Thousand Oaks, CA 91320 phone: 805499-5725 (US, CA) telex: 4994440 (US)

Bio-Rad Laboratories, Inc. 2200 Wright Avenue Richmond, CA 94804 phone: 800-4-BIORAD (US) phone: 415-234-4130 (US, CA) telex: 17-2128 (US)

Blackwell Scientific Publications, Inc. l?O. Box 50009 Palo Alto, CA 94303 phone: 415-9854081 (US)

Carl Zeiss, Inc. One Zeiss Drive Thornwood, NY 10594 phone: 914-747-1800 (US, NY) telex: RCA 221834 (US) telex: WU 84-8928 (US)

LKB-Produkter AB Box 305 S-181 28 Bromma Sweden phone: 08-98 00 40 (SW) phone: 301-983-3200 (US, MD) telex: 10492 (SW)

MJ Research, Inc. Kendall Square Box 383 Cambridge, MA 02142 phone: 817-924-1352 (US, MA)

Directory of Advertisers

p. IV PDGF, Inc. 812 Huntington Avenue Boston, MA 02115 phone: 817-738-5929 (US, MA)

P. v Stratagene Cloning Systems 3770 Tansy Street San Diego, CA 92121 phone: 800-424-5444 (US) phone: 819458-9151 (US, CA) telex: 9193809841 (US)

p. IX United States Biochemical Corporation p.0. Box 22400 Cleveland, OH 44122 phone: 800-321-9322 (US) phone: 2187856000 (US, OH) telex: 98-0718 (US)

P. t VCH Publishers, Inc. 220 East 23rd Street Suite 909 New York, NY 10010 phone: 212-883-8333 (US, NY)

p. VII

p. VI

P* x

pp. II, III

p. XI

p. VIII