50kV Voltmeter: Be very careful with this. It does work and is accurate enough for hobbiest work.Basics of High Voltage Probe Design: Covers theory, tips, pratical advice, sources, parts, links to other sites, and information about HV probes uses and design.Measuring high voltages: A fairly accurate safe way to measure really high voltages.Rectifiers and Electronics: Manufacturers of AC/DC high voltage and high current testing equipments, spark testers, industrial voltage stabilizers, AC and DC welding equipment, battery chargers. New Delhi, India.Sphere gap breakdown voltage tables: How to measure that HV with some precision.Vitrek: Manufactures hipot testers for both AC and DC measurements including a complete ground safety, fault locating, and measurement systems.