This presumption can be rebutted if the agreement is in writing and contains an express provision that it should be legally enforceable. Collective agreements are very common in the Swedish labour market and to a large extent regulate the relationship between an employer and his employees. A collective agreement (CBA) is a written legal contract between an employer and a union that represents employees. The CBA is the result of an extensive negotiation process between the parties on issues such as wages, hours of work and working conditions. The National Labour Relations Act, adopted in 1935, guaranteed workers the right to organize trade unions and to participate in such collective bargaining. .