61.  For unknown reasons, the group separated from their fellow hikers.

62.  Generally, surgeons operate on only one side of the brain, but for unknown reasons both sides of the body are affected.

63.  Her immune system, for unknown reasons, viewed it as an enemy and initiated a defense against it.

64.  However, even in the best hands, the operation itself sometimes triggers a stroke or heart attack, a complication more common in women, for unknown reasons.

65.  However, she said, the agency has heard that this flight has been delayed for unknown reasons and that there will be an unmanned mission instead this year.

66.  In the chapter the hero, Browne, repeatedly jumps ship for some unknown reason and then hauls himself back onto the boat.

67.  In recent years, and for unknown reasons, the level of subterranean waters in Moscow has steadily risen.

68.  Infectious prions are produced when normal prions, for unknown reasons, assume a flattened shape that prevents them from being broken down by the body.

69.  Instead, researchers found, the spinal nerve cells and surrounding tissue contain proteins which, for unknown reasons, inhibit any regrowth of damaged nerves.

70.  It is believed to be an early draft of the Declaration of Independence, later discarded for unknown reasons.