"prolonged efforts" is a correct and usable phrase in written English.
You can use it to refer to a period of time that is longer than others when you are devoting effort or attention to something. For example: "My prolonged efforts paid off when I finally secured the job I wanted."
Both the International Law Commission and the General Assembly undertook prolonged efforts that eventually resulted in agreement in 1974.
The doomed flight, carrying 94 people - 68 of them Iranian journalists assigned to cover military exercises in the southern port of Bandar Abbas - was scheduled to leave Tehran's Mehrabad airport at 7am, but did not depart until seven hours later following prolonged efforts to solve mechanical problems, according to local media.
In some cases, Yoo's condition of "specific intent" to commit acts of torture is clear from declassified interrogation logs, which reveal systematic and prolonged efforts to induce psychological states of debility, dependence and dread, euphemistically referred to as "ego down", "futility" and "fear up harsh".
Despite prolonged efforts aimed to correlate molecular composition and structural arrangements of humic substances with their biological activity on higher plants, the involved mechanisms of action are yet to be elucidated [4-7].
Before it could reach its destination the ship was trapped in pack ice, and by 14 February 1915 was held fast, despite prolonged efforts to free her.
"Too much reverberation," Mr. Weaver said after the reading, despite the prolonged efforts of audio engineers beforehand.
That is, in order for these little things to add up to meeting the big goals we have, there must be prolonged effort.
Since the majority of available conventional antibiotics do not exhibit prolonged effects, considerable efforts have been expended to demonstrate different antibacterial agents such as metal nanoparticles for wound dressings, drug delivery platforms, and tissue engineering scaffolds.
The vacancy presents a tantalizing opportunity for President Clinton, although one that could easily become entangled in the sort of ethnic and sexual politics that prolonged his efforts to staff the Cabinet.
It may also support previous experience that the combination of both epinephrine and vasopressin may be necessary to achieve the vasopressor response needed for restoration of spontaneous circulation, especially after asphyxial cardiac arrest or during prolonged CPR efforts.
Yet concerns over potentially prolonged permitting efforts have been mentioned before by others with knowledge of the New York projects.
