1) 很多时候，表达一个具体的时间或地点的名词词组不能用it代替：

错误：I went swimming in December, and John went swimming in it too.

错误：I ate dinner on the fourth floor, and John ate dinner on it too.

【答】有时候，语言表达出现错误，并不是语法上的错误，而是逻辑上的错误，或者不符合惯用法，或者啰嗦累赘，总之，错误在于不符合语言表达的基本规律。上两句被判错误，其实与it 指代的事物“是否具体”无关。因为第二个并列分句几乎完全重复了第一分句的内容，所以显得啰嗦、累赘，不符合语言的表达规则。可以改为简练的表达方式，如：and so did John. 

表达一个具体的时间或地点的名词词组，果真不能用it 代替吗？那么，我们把第二分句改一下，使用it 是完全可以的：

I went swimming in December, and it was not a very cold month here.

I ate dinner on the fourth floor, and it was crowded with people.

下面的Her birthday 和 His house，都是具体的时间或地点的名词词组，完全可以使用it 代替：

Her birthday is coming, and she is now preparing for it.

His house is small and dirty, but he likes it very much.

2) 然而如果是不够具体的时间或地点，就可以用it代替：

正确：Everyone who likes a winter month goes swimming in it.

正确：Everyone who likes a particular floor eats dinner on it.

【答】时间名词、地点名词，具体和不具体都没有关系，都可以使用it代替，见1)解答。

3) 具体的时间偶尔又可以用it代替：

正确：I spent June at the pool. It is my favorite month.

正确：I spent June at the the pool, but John spent it in his office.

【答】该问题仍然跟是否具体时间无关。不是“偶尔”，而是“很经常”，见1)解答。

其实，前3个问题是一回事，可以概括为一个内容。我认为，无论时间名词还是地点名词（包括表示其他事物的名词）表达的意思具体与否，当再次提到时，都可以使用it 代替。

4) 除了时间和地点，还有很多名词词组存在这种不能用it替代的现象。上世纪末Paul M. Postal曾对这些结构做过归纳，并将它们称为Antipronomial Context：

错误：He named his daughter Lucille, but I didn't name mine it.

正确：Everyone who dislikes their name wishes they were never named it.

错误：They painted their porch green, but I refused to paint my porch it.

正确：Everybody who likes some shade of green also paints their porch it.

【答】复合宾语中的补足语，一般不用it。这一句They painted their porch green, but I refused to paint my porch it. 中更是如此，it无法代替形容词green。

5) 有些结构又会解除这种不能用it替代的限制：

错误：John ate turkey on Thanksgiving. Jim ate turkey on it too.

正确：Every American who ate tofu on it remembers the Thanksgiving of 1977.

正确：Most Americans celebrate Thanksgiving. Some eat turkey on it.

正确：John avoids his family on Thanksgiving. Everybody else sees their family on it.

【答】第一句的错误重复了第一个问题的错误。后面的句子之所以正确，是因为句子的内容没有重复。例如：Most Americans celebrate Thanksgiving. Some eat turkey on it. 这句话说了两个内容：大部分美国人庆祝感恩节，在（感恩节）这一天有的人吃火鸡。

【个人观点】从这些问题看出，写这篇论文的作者过分注重了句子的外在形式，而忽略了句子的内容。因此，可能误导自己的观点。