21. But experts say nobody knows what the true incidence of deep vein clots on airplanes is, or how long people have to stay still to get one.
22. Experts say nobody knows what the true incidence of deep vein clots on airplanes is or how long people have to stay still to get them.
23. It was unclear how long people could be detained.
24. Jakubovits could not say how many people were affected by the evacuation order and said she did not know how long people had been ordered to stay away.
25. Levels of this enzyme can be abnormally low in people long exposed to tobacco.
26. The purpose of the study was to clarify the relationship between those factors influencing how long people live that can be modified and those that cannot.
27. There is a slow and irresistible movement, a surge of self-confidence of a people long placed in a situation of dependence.