1. While it is true that many voters change their minds several times before voting, and that some remain undecided until entering the voting booth, this is not true of everyone.

出处：

结构：While it is true that … this is not true of everyone (this does not apply to everyone).

翻译：的确，许多选民在投票前会反复，甚至有些直到进了选举亭才拿定主意，但是也不是每个人都这样。

2. Unless the author can demonstrate that the city will incur expenses that are not covered by the increased revenues from these projects, the author’s concern about these issues is unfounded.

出处：

结构：Unless the author can demonstrate that … the author’s concern about … is unfounded (groundless/unwarranted).

These concerns are unfounded. It is not necessarily a bad thing to hold a job for a short time; people may choose to change jobs frequently. Indeed, recent research by the Employment Policy Foundation, an American think-tank, suggests four-fifths of casual workers prefer the flexibility of temporary contracts. And lay-offs may be unpleasant for workers but will encourage them to switch quickly from failing firms in declining industries to successful ones in booming sectors.(the Economist, “The end of jobs for life?”, February 21, 1998)

翻译：除非作者可以证明，这些项目带来的收入的增加无法弥补该市为此付出的成本，否则作者关于这些问题的担心都是没有根据的。