When completing written assessments for this module, you are required to cite all your sources in the correct format. You should use the Harvard Referencing Style when citing sources. Guidelines are available at Introduction to Referencing and Plagiarism - CEMS Harvard Referencing Style - LibGuides at University of South Africa (UNISA). Determine, based on the above guidelines, which of the following options is/are correct when citing the prescribed book in the text of your assessment answers. Select one or more: According to PS Nel and M Kirsten (2020), trade unions exist to serve the interests of their members. Trade unions exist to serve the interests of their members (Nel, P.S. & Kirsten, M., 2020). Trade unions exist to serve the interests of their members (Nel & Kirsten, 2020). According to Nel and Kirsten (2020), trade unions exist to serve the interests of their members. According to Nel et al. (2020), trade unions exist to serve the interests of their members. Trade unions exist to serve the interests of their members (Nel, Kirsten, Erasmus, Gobind, Holtzhausen & Jordaan, 2020)