[en] The methods of nuclear data adjustment to be adopted in order to make them consistent with the integral information available, in recent years have developed to formulations quite similar in various laboratories, thanks to the common fundamentals of statistics theory on which they are based. There remain still unsolved, however, a number of problems which are closely connected to our poor ability of adequately representing the real physical situation (e.g., by inaccurate sensitivities, non linearities, etc.) or to negligence (systematic) errors in the cross-section data files. In the following, methods or procedures proposed for coping with these situations are reviewed