The following operators can be used in either the basic or the advanced search pages by entering them directly in the search box.

1.  "and"    "&"    "*"

Connecting words using "and" (or equivalents "&", "*"), or by using normal spacing between words, requires that the connected search terms occur concurrently in search results.

Examples:    legal and system
                       legal & system
                       legal * system
                       legal system

Such a search requires that "legal" and "system" exist concurrently in search results, but does not require that search results include the term "legal system."

2.  "or"    "+"    "|"

Connecting words using "or" (or equivalents "+", "|") requires that at least one of the connected search terms occur in search results.

Examples:    legal or system
                       legal + system
                       legal | system

Such a search requires that either "legal" or "system" exist in search results.

3.  "!"    "-"

Connecting words using "!" (or equivalent "-") requires that the term following the connector not occur in search results.

Examples:    legal ! system
                       legal - system

Such a search requires that "legal" exist in search results and that "system" not exist in the same search results.

4.  Phrase searching (using " ")

Putting search terms in quotations requires that such terms exist is the specified sequential order.

Example:    "commissioned customs declarations"

Such a search requires that search results include the exact phase found in quotation marks.

中文关键词中可使用的连接词：
1. “&”：意为逻辑“与”，指检索结果中必须全部包含其所连结的多个关键词。
2. “ and ”：同“&”。
3. “ ”（空格）：同“&”。
4. “*”：同“&”。
5. “+”： 意为逻辑“或”，指检索结果中将包含其所连结的某一个或多个关键词。
6. “ or ”：同“+”。
7. “|”：同“+”。
8. “!”：意为逻辑“非”，指检索结果中包含其连结的前一个关键词，但不能包含其连结的后一个关键词。
9. “-”：同“!”。