Limitations

A or one significant problem is …

… is a serious obstacle to …

The problem is a complex one.

There are obvious limitations to or in …

… can only be adequately explained by …

… is beyond the scope of this study

whether … also applies to … is unclear

the precise or exact mechanism for or of … remains unclear

practical implementation of … poses a number of problems

The question remains, however, …

What the study is unable to say is …

This study does not claim to be able to …

It would be rash to conclude from this that …

It is still uncertain whether …

… remains an open question

It remains to be seen whether …

It would be unwise at present to …

Nevertheless, it must be emphasized US and GB or emphasised GB that …

We should stress that these results are only provisional.

As with all such studies, there are limitations that offer opportunities for further research.

further work or research is required in order to …

further work or research is necessary before we can …

much work remains to be done on …

… requires a great deal of further research

… remains a considerable challenge to or for …

At present, these or such goals seem remote.

Next: Implications and applications

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