First, the first layer is Chinese characters with numbers and pauses, such as "one", "two" and "three".

Second, the second layer contains Chinese characters and numbers in brackets, such as "(1)", "2" and "3".

Third, the third layer is Arabic numerals with footnotes, such as "1", "2" and "3".

Fourth, the fourth layer contains Arabic numerals in brackets, such as "(1)", "2" and "3".

The fifth layer is circled Arabic numerals, such as ①, ②, ③ or 1), ② and ③.

The sixth floor is capitalized English letters, such as "A", "B", "C" or "(A)", "B" and "C".

The seventh layer is lowercase English letters, such as "A." "B." "C." or "(A)" "B" and "C".

Extended data:

Precautions for use:

First, Arabic numerals are followed by black dots;

Second, there is a pause after Chinese characters and numbers;

3. Use commas after "first", "second" and "third";

Four, the serial number in brackets and the serial number in the circle, no longer followed by pause, comma, etc.;

Five, the first part, the first chapter, the first section or "one" does not need punctuation, and there is a Chinese character position between it and the following text.

Six, before and after the digital serial number generally no longer use other bullets.

Baidu Encyclopedia-Serial Number