Using booking class in ITA matrix is not an option, because, as in case of Aeroflot, we can choose between refundable and non-refundable fare within the same booking class, with only a marginal difference in the price.

I'm not familiar with the fare structure of the other airlines so I don't know what kinds of fares to search for. Are there any keywords to put in ITA matrix in order to specify only refundable fares to be used?