This question has been much disputed, and is difficult to test, not least because of the sheer number of interactions to assess: tens of millions of changes in DNA have been observed in the human genome, and so there are many more than billions of possible combinations of these changes to investigate.
Some texts suggest that, no matter how zealous its membership was, Al Qaeda had some of the same failings that afflict many organizations -- petty infighting, internal policy disputes and difficult relations with other organizations, in this case the Taliban.
The modernist composer Charles Wuorinen has disputed the label "difficult," which is invariably assigned, alongside "thorny" and "serial," to much of his music.
The year 2013 in Belarus brought some fairly typical disputes with Russia and difficult times for the economy.
Be wary of radically differing lifestyles because they often signal differing tastes and ultimately lead to the most frustrating and difficult disputes.
Empirical evidence that would adjudicate this dispute is surprisingly scarce and difficult to interpret.
The respondents told of the loss of a newborn child, the death of several relatives within a short space of time, unsuccessful adoption processes, and difficult child custody disputes.
The dispute proved difficult, and the IOC initially voted to cancel the tournament and eliminate ice hockey as an Olympic sport, but relented as thousands of tickets had been sold by the organizers.
Since moving to live with his father, Rocco has been attending school in London but Ellen Sigal, a court-appointed attorney for the 15-year-old, said he was finding the family dispute "very difficult" and was keen for it to come to an end immediately.
