Extensive search

You can modify your search operations in such a way that you search for a specific subject, publication or author. Using Boolean, wildcard and proximity operators you can modify a general search operation so that the search more closely approximates your expectations.

	Search using search operators
	Search for approximate matches
	Mandatory and non-mandatory terms
	Parentheses: nesting a search operation
	Combining Search operators: complex search operations
	Articles, prepositions and other fill words
	Overview of search operators

1.  Search using search operators

The search engine supports the following search operators:

	Boolean operators
	Wildcard operators
	Proximity operators

With these operators you can modify search operations in such a way that the search results more closely approximate your expectations.

1.1  Boolean operators

Sometimes a search operation is too general (results in too many matches) or too specific (results in too few matches). You can use Boolean operators to modify your search operations. You can initiate a Boolean search operation by entering one or more search terms in the search bar in combination with the operators AND, OR and NOT (capital letters have no effect):

	AND, &		If you have used a search term that is too general, you can combine different search terms using AND. By combining search terms in this way, you can further restrict your search and reduce the number of search results. For example: einstein AND gravity searches for all titles that contain both einstein and gravity.
	OR, |		To broaden your search operation, you can combine search terms by using OR. This method searches for you search terms both simultaneously and independently. For example: einstein OR gravity searches for all the titles that contain either einstein or gravity or both.
	NOT, -		To restrict a search operation you can combine search terms by using NOT. This excludes specific subjects from your search results. For example: einstein NOT gravity finds all titles that contain einstein but not the term gravity.

1.2  Wildcard operators

Using wildcard operators you can search for words using 'variables'. For example: words that appear in more than one spelling, such as organization and organisation.

You can place a wild card in the middle or at the end of the search term. You cannot place a wildcard at the beginning of a search term.

Using the following wildcard operators you can replace characters in search terms:

	?, *		Replaces a random number of characters. For example: use* will find use, user, user-friendly; organi*ation will find organisation and organization.
	#		Replaces no or one character. For example: use# will find use, used, but not useful or user-friendly.
	!		Replaces one character. For example: use! will find used, but not use or users.

You can combine wildcards within a search term. For example: micro?p* will find microcomputer, microscope, microprocessor, etc.; micro!p* will find microsphere, microoptics, etc. Wildcards can also be used in combination with figures. For example: 199#.

1.3  Proximity operators

The search engine supports the use of proximity operators. Using proximity operators you can replace one or more search terms in a search operation.
Below is a list of proximity operators and a brief description of their use:

	?, *		Replaces a random number of words; searches from left to right. For example: use ? drugs finds use of drugs, but also the use of different types of drugs.
	#		Replaces no or one word; searches from left to right. For example: use # drugs finds use of drugs, but does not find use of different types of drugs.
	!		Replaces one word; searches from left to right. For example: use ! drugs finds use of drugs, but does not find use of different types of drugs.
	%		Searches titles whose sequence is not specified. For example: john % kennedy finds John Kennedy, but also Kennedy, John. Ensures that an operator that normally searches from left to right can also search from right to left. For example: john #% kennedy not only finds John Kennedy and John F. Kennedy, but also Kennedy, John and Kennedy, John F.
	NEAR, ~		Searches titles in which the first search term is encountered within three words of the following search term; searches in two directions. For example: money NEAR spend finds titles in which two or fewer words is between money and spend. Moreover, it is possible to specify the number of intervening words using NEAR/N. For example: money NEAR/3 spend finds titles in which three or fewer words are between money and spend.

You can also combine Boolean, wildcard and proximity operators. For more detailed information on combining search operators, see Combining Search operators: complex search operations.

2.  Search for approximate matches

You can search for approximate matches using the /n operator. By adding /n to the search term you can specify how many 'variables' are allowed in the search term, where n stands for the number of variables. Each addition, deletion or replacement of a character counts as a variable.

For example: rachmaninov/2 finds titles that contain two variables or less, such as rachmaninov, rachmaninoff and rachmaninow. However, for technical reasons the first three characters must be correct, which means that this search operation will not find ragmaninov.

3.  Mandatory and non-mandatory term

Your can precede a search term by the + character. This means that this word is mandatory. Your can also precede a search term by the - character. This means that this word must not appear.

For example: transport -auto finds all titles that contain the word transport, but do not contain the word auto.

4.  Parentheses: nesting a search operation

You can also use parentheses in a search operation. Without parentheses, a search operation is performed according to the hierarchy of the search operators. That is, the operator that is highest in the hierarchy takes precedence. Proximity operators have the highest position in the hierarchy, followed by AND and then OR. Parentheses ensure that the search engine can ignore this hierarchy. This enables you to nest your search operations.
For example: (auto OR bicycle) AND (transport OR highway) finds titles that contain auto and/or bicycle and that also include transport and/or highway.

5.  Combining Search operators: complex search operations

It is possible to compose complex search operations by combining search operators such as Boolean, wildcards and proximity operators.

• Example 1: complex search operation
  NOT johann ? bach searches for titles that contain the word bach not preceded by the word johann. This search operation will not find a title containing johann sebastian bach, because in this title johann precedes bach. This search operation will find the title wilhelm bach, johann bach because the title contains an occurrence of bach not preceded by johann.
• Example 2: complex search operation
  Einstein ##! gravity searches for titles that contain einstein and gravity with three or less intervening words. A search operation with einstein NEAR/3 gravity searches for titles that contain einstein and gravity (or gravity and einstein) with three or less intervening words.
• Example 3: complex search operation
  Einstein #### gravity finds titles that contain einstein and gravity with four or less intervening words. Another possibility for finding the same result is: einstein #/4 gravity.

6.  Articles, prepositions and other fill words

Every word in a title is indexed with the exception of fill words. Fill words are words that are ignored during a search operation to prevent irrelevant information from being displayed. Articles, pronouns, adjectives, adverbs and prepositions are examples of fill words. Words that appear, but have no relevance during a search operation. For example: the, him, a, of, in, etc.

7.  Overview of search operators

Below is an overview of the search operators supported by the search engine:

	AND, &		Boolean operator; searches in two directions; finds titles that contain both words. For example: einstein AND gravity.
	OR, |		Boolean operator; searches in two directions; finds titles that contain either of the two words or both of them. For example: einstein OR gravity.
	NOT, -		Boolean operator; searches in two directions; finds titles that contains the first word, but not the second. For example: einstein NOT gravity.
	NEAR, ~		Proximity operator; searches in two directions; searches for words that are located in close proximity. For example: money NEAR spend. Moreover, it is possible to specify the number of intervening by using NEAR/N. For example: money NEAR/3 spend.
	/n		Search operator; searches for approximate matches by adding /n to the word, where n stands for the number of 'variables' permitted. For example: gorbatsjov/3.
	"		Searches for the exact phrase entered between the quotation marks. For example: "fourth symphony".
	?, *		Wildcard operator; replaces a random number of characters. For example: use? or use*. Proximity operator; searches from left to right; replaces a random number of words. For example: use ? drugs or use * drugs.
	#		Wildcard operator; replaces no or one character. For example: use#. Proximity operator; searches from left to right; replaces no or one word. For example: use # drugs.
	!		Wildcard operator; replaces one character. For example: use! Proximity operator; searches from left to right; replaces one word. For example: use ! drugs.
	%		Searches titles for which the sequence of the words is not specified. For example: john % kennedy. Ensures that an operator that searches from left to right also searches from right to left. For example: john #% kennedy.
	+		Search operator; searches titles that at a minimum contain the added word. For example: +auto bicycle.