Yet amid his discussion of 11-dimensional space-time and the difficulties of uniting general relativity with quantum mechanics, Mr Greene is refreshingly candid about the fact that superstring theory is still unproven, an admission that does nothing to diminish the reader's enjoyment.
But the difficulty of United's task was frequently exposed.
This would be attending to the human climate of divisiveness so we might fear less facing the prospect of uniting to deal with the physical realities facing our more global climate difficulties.
They show no immediate prospect of uniting.
Over the last 20 years, United has weathered strikes, takeover attempts and management disputes, and there are few who would know more about the difficulty of running United than Richard J. Ferris.
The Kurds are resisting, underscoring yet again the depth of ethnic and sectarian divisions here and the difficulty of creating a united Iraq even when overall violence is down.
But in the wake of last week's stunning defeat of legislation to replace the Affordable Care Act, which further eroded his already flagging poll numbers, Mr. Trump has made an abrupt shift from courting his party's most conservative lawmakers to hurling threats at them, a vivid illustration of his difficulties uniting a still-riven Republican Party.
There were also immense long-term difficulties in uniting the previously disjointed territories.
In addition to the obvious difficulty of applying a United Kingdom-based model to the South African setting, it is also probable that the treatment of diabetes, and its co-morbidities, has improved substantially since the engine was developed (the intervention trial on which the engine is based was completed in 1997 and the post-trial programme ended in 2007) [ 43].
The initial challenges to inferring evolutionary relationships among the ditrysian superfamilies have been attributed to their morphological homogeneity, and thus to the difficulty of finding distinct, unique morphological characters uniting superfamilies and supporting descent from a common ancestor [ 2, 13].
