The reason for this variation has not been established conclusively.

The reason for the damage had never been established.

No reason for the loss was officially established.

The reason for the low speed was never established.

The whole reason for the clan having been established in the first place, back at the dawn of time.

The reasons for the raid have never been established.

The reasons behind this were never established, though it was suspected some rumours might have been started by rival institutions.

The reason for the collapse was never established, but a possible cause was the nature of the lime used to make the mortar.

The reason for the shooting was never fully established.

The reason for the transfer was never clearly established.