(1) the balance when it comes to applying qualitative, quantitative or both research methods (number of them) ? (2) Which methods are more efficient (whether it is better to use quantitative research methods first supplying them by qualitative ones or other way) ? (3) Where is the limit for expanding our research – is it infinite ? (4) Where is the so-called endpoint for analysis processing ? (5) Does aforementioned limit of using additional research methods exist ? (6) How important the triangulation of research methods is ?