Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Related work has reported problems with spammers and unethical workers, who produce incomplete or absurd output (Feng et al. 2009, Mason & Watts 2009, Kazai, G. 2011). In our experiment, for example, text fields were provided for writing down each question based on investigations in Aker, El-Haj, Albakour & Kruschwitz (2012) who report that text fields are a good design selection in order to detect unwilling or less careful workers.
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