In the renormalizable theory of weak interaction, Kobaishi and Maskawa investigate CP-violation. They conclude that no realistic models of CP-violation exist in the quartet scheme without introducing new fields. They discuss possible models of CP-violation. When applying the renormalizable theory of weak interaction to hadrons, limitations on the hadron model arise. The triplet model has difficulties with strangeness-changing neutral currents, while the quartet model is free from this. Maki and Maskawa showed that the strong interaction must be chiral SU(4) × SU(4) invariant in the quartet model. For the theory to be realistic, CP-violating interactions must be incorporated in a gauge-invariant way, imposing further limitations. The paper investigates the quartet model with charge assignments for p, n, λ, and ζ. The Lagrangian is divided into kinetic, mass, strong interaction, and residual interaction parts. The mass term includes couplings with a scalar field φ, which can violate CP-conservation. After eliminating Goldstone modes, residual interactions remain. The mass term can be simplified by applying a gauge transformation. The quartet field is assigned to representations of SU(weak)(2). The cases (A, C), (A, B), (B, B), and (A, A) are considered. In the (A, C) case, CP-violation is possible if additional fields are introduced. In the (A, B) case, CP-violation is possible through the weak current, but experimental constraints limit this. In the (B, B) case, CP-violation is possible but contradicts experimental results. In the (A, A) case, no CP-violation occurs if L' = 0. The paper discusses possible models of CP-violation through L'. Introducing another scalar field ψ can cause CP-violation. A scalar field S mediating strong interaction can also cause CP-violation. A 6-plet model is considered, where CP-violation appears in non-leptonic processes but not in others. The authors conclude that no realistic models of CP-violation exist in the quartet scheme without introducing new fields. Other models, such as Georgi and Glashow's, incorporate CP-violation without introducing new fields.In the renormalizable theory of weak interaction, Kobaishi and Maskawa investigate CP-violation. They conclude that no realistic models of CP-violation exist in the quartet scheme without introducing new fields. They discuss possible models of CP-violation. When applying the renormalizable theory of weak interaction to hadrons, limitations on the hadron model arise. The triplet model has difficulties with strangeness-changing neutral currents, while the quartet model is free from this. Maki and Maskawa showed that the strong interaction must be chiral SU(4) × SU(4) invariant in the quartet model. For the theory to be realistic, CP-violating interactions must be incorporated in a gauge-invariant way, imposing further limitations. The paper investigates the quartet model with charge assignments for p, n, λ, and ζ. The Lagrangian is divided into kinetic, mass, strong interaction, and residual interaction parts. The mass term includes couplings with a scalar field φ, which can violate CP-conservation. After eliminating Goldstone modes, residual interactions remain. The mass term can be simplified by applying a gauge transformation. The quartet field is assigned to representations of SU(weak)(2). The cases (A, C), (A, B), (B, B), and (A, A) are considered. In the (A, C) case, CP-violation is possible if additional fields are introduced. In the (A, B) case, CP-violation is possible through the weak current, but experimental constraints limit this. In the (B, B) case, CP-violation is possible but contradicts experimental results. In the (A, A) case, no CP-violation occurs if L' = 0. The paper discusses possible models of CP-violation through L'. Introducing another scalar field ψ can cause CP-violation. A scalar field S mediating strong interaction can also cause CP-violation. A 6-plet model is considered, where CP-violation appears in non-leptonic processes but not in others. The authors conclude that no realistic models of CP-violation exist in the quartet scheme without introducing new fields. Other models, such as Georgi and Glashow's, incorporate CP-violation without introducing new fields.