There are two situations. In one case, the quoted sentence is complete and used independently. In this case, the period at the end of quotation marks should be enclosed in quotation marks. For example:

"Words without words are not far away." Many famous science books are both literary and easy to understand. Therefore, it is widely circulated.

Quotation marks are used independently, the sentences in quotation marks are complete, and the period marks the end of the quotation marks in quotation marks, so it should be placed in quotation marks. In other words, this period is the period of quotation independent of the sentence.

In another case, quotation marks are part of the whole sentence, and then the period should be placed outside the quotation marks. For example:

These situations vividly show that articles lacking in literary talent are indeed "words without sentences, but not far away."

Quotes, not used independently, are part of the whole sentence, so put a period outside the quotation marks and let the period mark the end of the whole sentence. In other words, this period is the period of the whole sentence, not the period of the quotation.

The sentence related to "so-and-so" involves the period and comma before the back quotation mark.

A comma should be used after the inserted "so-and-so".

The word before "so-and-so" can be a half sentence or a sentence. When it is a half sentence, a comma is usually used, such as "

"He went to Beijing yesterday," said his brother. "He will come back next month."

"He went to Beijing alone!" My brother said, "Why didn't you say hello to me?"