There is a need for more long term studies to determine whether the drug is safe and the effect sustained over longer periods.

她说，尚需一个较长期的研究，以确定这种药物的安全性以及长期影响。

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That the recovery cannot be sustained over the long term without health care reform.

CNN: Economic uptick plays key role in health care debate

Partner capacity can only be sustained over the long-term when partner governments have the political will, absorptive capacity, credible and effective institutions, willingness to independently sustain U.S. investments, an equal stake in the success of security sector initiatives, and policy commitment to security sector reform.

WHITEHOUSE: Fact Sheet: U.S. Security Sector Assistance Policy

And a sustained effort at investing in our infrastructure could put a lot of people back to work and make us more competitive over the long term.

WHITEHOUSE: Open for Questions with President Obama