If you are citing not yet published material, define these works from others with a suitable remark in your citation. This applies for e.g. scholarly articles waiting to be published. Include all available information, e.g. publisher and journal title.
Carlson, H. (2019). Postmodernism. [manuscript]. Helsinki: Hanken School of Economics.
Karlsson, H. (2015). Trends in tourism [pre-print]. Tourism and Hospitality Research.
Karlsson (2015 p. 10) claims that…