Acontractisanagreementbywhichtwopartiesmutuallypromisetobuyorsellsomeproducts.Inpractice,someinformalcontractsmaybereachedorally.Thisisunderstandable,butmayleadtounfortunateconsequences.Areasonableexportershouldatleastinsistonstrictobservanceofthelegalrequirementsincaseofordersthatarenotroutinetransactions.Whenthegoodsorderedrepresentaconsiderablevalue,aformalcontractembodyingalltermsoftheagreementshouldbepreparedinduplicate；eachcopyshouldbesignedbybothparties,andeachpartyshouldretainacopyofthecontract.