《Collins Cobuild英语语法大全》第465页8.111

要对所说的事进行补充时，往往可用由介词加 ‘which’再加名词引出的非限制性关系从句，名词通常为 ‘time’或 ‘point’等词，或 ‘case’、 ‘event’等泛义词。

They remain in the pouch for some seven weeks, by which timethey are about 10cm long.

I was told my work was unsatisfactory, at which pointI submitted my resignation.

Sometimes you may feel too frail to cope with things, in which casedo them as soon as it is convenient.

《朗文英语语法》(L. G. 亚历山大编著) 第41页

which意谓this或that时，也可用于in which case, at which point, on which occasion等说法；表示整个小句：

I may have to work late, in which caseI’ll telephone.

我可能得晚点下班，那样我会打电话的。

The speaker paused to examine his notes, at which point a loud crash was heard.

讲演者停下来查阅他的笔迹，就在此时，听到了砰的一声巨响。

《牛津英语用法指南》（第三版）第761页

which在关系从句中可以用作限定词，与一个重复前面意思的普通名词连用。这种结构相当正式，主要用在介词后面，尤其在in which case和at which point这样的一些固定短语中。

She may be late, in which casewe ought to wait for her.

她可能会迟到，那样的话我们应该等她。

He lost his temper, at which pointI decided to go home.

他发脾气了，这时候我决定回家。

He was appointed Lord Chancellor, in which post he spent the rest of his life.

他被任命为大法官，在这个职位上度过了他的余生。

《柯林斯高级英语用法词典》第754页

非限定性关系从句可以用“介词+which+名词”引导。这种情况唯一的常用句型是in which case, by which time和at which point。

It may be that your circumstances are different or unusual, in which case we can ensure that you have taken the right action.

可能你的情况不同或特殊，在这种情况下我们向你保证你采取了正确的行动。

Leave the whole thing to cool down for two hours, by which time the spices should have thoroughly flavoured the vinegar.

让它整体冷却两小时，到那时香料的味道就会完全溶解在醋里。

《英汉多功能学习词典》第1637页which词条

which（关系形容词）（非限制性用法，正式）而且（或可是）那个

He was born in Chicago, in which city he died. 他出生于芝加哥，又死在那里。

（可以用where来代替which city，但使用介词可以表示出先行词是市还是镇等这种细微意义上的差别）

He came back eight months later, by which time (by the time he came back) the Japanese side had decided to say yes.

八个月后他回来了，在此之前日方已经决定同意。

《麦克米伦高阶英汉双解词典》第2390页which词条

The search will not begin until dawn, by which time it will probably be too late.

搜查要到黎明时才开始，到那时候恐怕太晚了。

in which case (= if this happens)如果是那样的话

Of course it may rain, in which casewe shall have to hold the ceremony indoors.

当然可能会下雨，如果那样的话我们讲不得不在室内举行仪式了。

《现代英语用法词典》（修订版）第1814页which词条

which有时在从句中作定语。

My father may have to go into hospital, in which case he won’t be going on holiday.

I called him by the wrong name, for which mistake I apologize.

Tom spent four years in college, during which timehe learned French.

《当代高级英语语法》（徐广联主编）第919页

Ten years of hard work changed her greatly, for which reasonhe could hardly recognize her at first sight. 10年辛劳使她变化很大，一见之下很难认出她来了。

《朗文当代高级英语辞典》第四版第2627页which词条3

《朗文高级英语应试词典》第2704页which词条3

She may have missed the train, in which case (= if this happens) she won’t arrive for another hour. 她可能没赶上火车，要是那样的话她还要过一个小时才能到。

《朗文高级英语应试词典》第324页case1词条2

He won’t want to eat it unless he’s really hungry, in which casehe’ll eat almost anything.

除非很饿，否则他不会吃东西，一旦饿了他几乎什么都吃。

《麦克米伦高阶英汉双解词典》第306页case1词条2

case: （尤指涉及特定之人或事的）情况，状况

They had the choice to comply with the conditions, in which case the bombing would have stopped. 他们可以选择顺从实际情况，这样的话轰炸本来是可以阻止的。

《柯林斯高阶英汉双解学习词典》第385页case词条12

in that case or in which case那样的话；在那种情况下

Perhaps you’ve some doubts about the attack.In that caseit may interest you to know that Miss Woods witnessed it. 你也许对这起袭击还有些怀疑，那么如果我告诉你伍兹小姐亲眼目睹了这起事件，你可能会感兴趣。

Members are concerned that a merger might mean higher costs, in which case they would oppose it.

成员们担心合并会导致成本提高，若是那样的话，他们将提出反对。

The temperature will rise to 33 degrees Fahrenheit, at which pointthe ice will begin to melt.

They remain in the pouch for some seven weeks, by which timethey are about 10cm long.

I was told my work was unsatisfactory,at which point I submitted my resignation.

Sometimes you may feel too frail to cope with things, in which case do them as soon as it is convenient.