Ohio-based Paid Search Engine Tools sued Google, Microsoft, and Yahoo in the Eastern District of Texas, alleging that its paid-advertisement services infringed one of its patents. District Judge David Folsom ruled in favor of the search engines that invalidated a patent related to paid-advertisement services. The judge said the patent was not valid based on prior art. Attorneys for Paid Search filed suit against Yahoo in September 2007, claiming that Yahoo Search Marketing infringed its patent related to paid searches. The company later sued Google and Microsoft.