The San Gabriel Valley Tribune, Pasadena Star-News and Whittier Daily News announced the layoffs of 31 workers companywide as part of the sale of the three daily newspapers. Toronto-based Thomson Corp. last month said it would sell the newspapers to Denver media executive Dean Singleton, whose MediaNews Group takes control of the papers Friday. Singleton said 530 employees will remain at the papers, which will retain separate names and editorial identities. Singleton said he expects to expand the reporting staff to boost local coverage. The papers have a combined daily circulation of 119,000.