Complex sentence: Osram, Philips, Tungsram, Associated Electrical Industries, ELIN, Compagnie des Lampes, International General Electric, and the GE Overseas Group were members of the Phoebus cartel, holding shares in the Swiss corporation proportional to their lamp sales.
Split into simpler sentences: Osram, Philips, Tungsram, Associated Electrical Industries, ELIN, Compagnie des Lampes, International General Electric, and the GE Overseas Group were members of the Phoebus cartel. They owned shares in the Swiss corporation proportional to their lamp sales.