If you cite the author(s) in the text, it is not necessary to repeat the name(s) in the parentheses. The source reference will look like this:
According to Grit (2021), there are different behavioral types. For example, you have introverts, extroverts, thinkers and feelers and you can classify these types back into behavioral colors.
- two authors - in the text use the word 'and' between the names instead of an ampersand
The study followed the methods described by Fischer and Julsing (2019).
- three and more authors - use the Latin 'et al.':
According to Broekhoff et al. (2015), market research is when it involves markets or customers and products or services.