Normally, the transferable knowledge across domains are derived from some certain data, while others contribute less and are costly to be learned from (Axelrod et al., 2011;Ruder and Plank, 2017).
previous studies conduct domain adaptation through selecting relative and informative source data according to the nature of the target domain, via entropy-based methods , Bayesian optimization (Ruder and Plank, 2017), etc.