Because this unit varies from a few metres to tens of metres, from clays to laterites, sandstones or limestones, and from conglomerates to breccias, it is often very difficult to define its precise position solely from the examination of cuttings.
It is often very difficult to interpret even in its original print.
It is often very difficult to distinguish between bronze and brass merely by their appearance.
"It is often very difficult to gain consensus on the numbers of casualties in Iraq.
However, it is often very difficult to obtain corresponding precise data and information in advance due to insufficient data, changing environment or new components.
Each of these generic groups, however, is highly polymorphic, so that it is often very difficult for the operator to classify individual axes with absolute confidence and certainty.
Given our system, it is often very difficult if not impossible to predict the consequences of our voting, beyond increasing one candidate's chance of election.
It is often very difficult to decide this question, because knowledge of human beings is insufficient or because the dramatist himself has not provided enough clues.
Even after two or three rounds of a major, it is often very difficult (if not impossible) to predict what is going to happen.
A second, linked problem is that even when the underlying principle has been identified, it is often very difficult to put into use.
Network providers work extremely hard to keep the financial details of their peering arrangements secret, so it is often very difficult to know who's paying whom and how much.
