The Finnish Industrial Federation and UPM Plywood are negotiating a company-specific agreement.    The strike has stopped UPM's plywood mills in Ristiina, Savonlinna and Joensuu, as well as the Kalso veneer mill in Valkeala, Kouvola, reports the Finnish newspaper Maaseudun Tulevaisuus .    The labor dispute concerns a company-specific collective agreement that the Finnish Industries Federation is negotiating with UPM Plywood.    The strike that started last Monday will last until the end of the day on Sunday. The next strike is scheduled to start immediately after Monday and ...