Searching for Papers

Searching for Papers

You need to give the search engine a grep regular expression for effective searches. Don't worry if you are not familiar with how a grep regular expression is put together, because this is what this tutorial is meant for. Then again if grep expressions are old hat to you, by all means, search to your heart's content!

Note:The search now supports boolean expressions (for the papers section only).

Simple Word Search
If you are only searching for a word or name that is purely alphanumeric, that is, either letters (a-z) or digits (0-9), then the search is fairly straightforward. For example, if you want to search for fractal in the database, simply type:

fractal

If the expression you are looking for contains two or more words, then again simply type it in. By the way, the search is case insenstive. For example:

fractal basin boundaries

Search using Escape characters
In grep regular expression, there are some characters that have special meanings. For example, the period "." is a special character that matches any character (sort of like the wildcard character "?" when you work with UNIX files and directories). In order to search for it, you need to escape its special meaning by typing a "\" in front of it. For example, if you want to search for papers by E.D. Yorke and not J.A. Yorke, type:

E\.D\. Yorke

Be careful, the above will find "E.D. Yorke", but not "E. D. Yorke", Barring any misentries, the listing's format is of the form "F.M. Lastname". Some other special characters you should keep in mind when searching are "*", "[", "]", "-".

Search using "OR"
To perform an OR search, you use the special character "|". It is also wise to enclose your choices in brackets. For example, if you want to search papers with "strange" or "attractor" in it, you type:

(strange|attractor)

The reason for the brackets can be seen from the following common mistake. If you want to look for any papers with "strange attractor" or "chaotic attractor", don't type "strange| chaotic attractor", because it will only look for "strange" or "chaotic attractor", instead, type:

(strange|chaotic) attractor

Search using "AND"
In grep, there is no real AND search, but you can simulate it with the special characters ".*" which matches any number of any character (equivalent to "*" for UNIX file systems). The problem is that you need to be careful about the order of your search. For example, "grebogi.*yorke" matches any paper where Grebogi's name appear ahead of Yorke's, but it misses papers where Yorke appears in front of Grebogi (I know it's rare but it's not nil!). To cover your basis, you can combine it with "|", that is:

(grebogi.*yorke|yorke.*grebogi)

Some More Tips
Caveat: The following tips only apply to database of papers by University of Maryland Chaos Group and Collaborators. The huge chaos database provided by Peter Beckmann is set up differently.
When doing complex searches, keep in mind that the way the paper is referenced is in the following order:

Authors, "Title", Journal Name, Vol. No., Pg. No., (Year).

If you are fairly sure about the article, you can type something like:

(grebogi.*yorke|yorke.*grebogi).*crises.*(Phys. Rev|Physica D).*199[0-3]

Here, you want some papers on crises that is written by at least Grebogi and Yorke, and it appears in either Phys. Rev. series or Physica D between the years 1990-1993. Phew!

Boolean Expressions
(This section is adapted from the htgrep's help section).

For more control over the search query, you can use a boolean expression. If you enter the word or between two search words (with a space between each word and the "or") it will find any record which contains either the first word, or the second word, or both. For example, "chaos or fractal" would find records containing the word "chaos" or the word "fractal", or both.

If instead of the word or you entered and it would match only records which contained both the word "chaos" and the word "fractal". Note that this would be the same as a simple search for "fractal chaos" because if the boolean commands are omitted, it defaults to assuming an and between each search word.

To find records which do not contain a particular word, place the word not before it. For example, "not attractor" would find all the records which do not contain the word "attractor". You can combine the "and", "or" and "not" commands, for example "chaos and not attractor" would find records containing the word chaos but not the word attractor.

For advanced use, you can use brackets to group the expression. For example, "chaos and (embedding or dimension)" would find all records containing the word "chaos" and either "embedding" or "dimension" (or both). If the brackets are omitted, the and command has higher precedence, so "chaos and embedding or dimension" would find all records contain "chaos" and "embedding", and also records containing "dimension".

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