Complex sentence: In 1947, Siegel and Shuster sued the successor company National Comics Publications for $5 million and the rights to both Superman and Superboy, arguing National had no rights to Superboy because it had effectively rejected it by not accepting it within six weeks of submission.
Split into simpler sentences: In 1947, Siegel and Shuster sued the successor company National Comics Publications for $5 million and the rights to both Superman and Superboy. They argued that National had no rights to the Superboy character because it had effectively rejected it by not publishing it within six weeks of submission.