In this Letter, we study Kaup-Boussinesq system by using the wellknown He's variational approach. In fact, the He's variational method is a promising method to various systems of linear and nonlinear equations.

Introduction: The use of animals in experiments and their role in the development of medical sciences are undeniable. Humane endpoints terminate pain and distress in laboratory animals, which are experimented in painful procedures and an involuntary manner. This study was going to review studies published in this area to assist researchers in developing their approach. Methods: Articles used in this review study were obtained from relevant databases including Pubmed, Scopus, Science Direct, OVID, SID, Magiran and Google scholar. Results: “Humane endpoints” or killing the animal humanely means the point at which an experimental animal’s pain and/or distress is terminated. This pain and distress are not necessarily accompanied by clinical symptoms and it can also be recognized by biochemical, physiological and molecular biomarkers testing. Conclusion: Regarding the extensive use of laboratory animals, the aim is not only to take care of animals but also to develop knowledge and prevent unintentional animal suffering and death. Increasing awareness of ethical issues regarding research animal use needs scientific information and designing experiments, which are terminated immediately after achieving main goals. Otherwise, it threatens the life of animal and leads to the animal suffering.

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