Critics claim that the legal principle of laches, hence not asserting one's rights in a timely manner, invalidates Forgent's claims on the patent. They also noted the similarity to Unisys' attempts to assert rights over the GIF image compression standard via LZW patent enforcement. The JPEG committee responded to Forgent's claims, stating that it believes prior art exists that would invalidate Forgent's claims, and launched a search for prior art evidence. The 1992 JPEG specification cited two earlier research papers written by Wen-Hsiung Chen, published in 1977 and 1984. JPEG representative Richard Clark also claimed that Chen sat in one of the JPEG committees, but Forgent denied this claim.