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i want to add urls in my reference

i am using the following code in my .tex file

    \bibitem{bl}Business Logic layer, \url{http://en.wikipedia.org/wiki/Business_logic_layer}, 23 12 2011.

however, i get the following output in my console

    ! Undefined control sequence.
    l.477 \bibitem{bl}Business Logic layer, \url

    ! Missing $ inserted.
    <inserted text> 
    l.477 ...rl{http://en.wikipedia.org/wiki/Business_
                                              logic_layer}, 23 12 2011.
    ! Extra }, or forgotten $.
    l.477 ....wikipedia.org/wiki/Business_logic_layer}
                                              , 23 12 2011.

    ! LaTeX Error: Command \item invalid in math mode.

whereas my .pdf file entry against this code is this.

    Business Logic layer,

http://en.wikipedia.org/wiki/Businesslogiclayer; 23122011

what is this error about and how can i set this right?

share|improve this question
Have you loaded the url package? – Seamus Jan 6 '12 at 8:58
Loading the hyperref should also work, i.e., make the command \url available. – Mico Jan 6 '12 at 9:02
@Mico that's because hyperref loads url – Seamus Jan 6 '12 at 9:16
i m a newbee with latex so trying to learn its tricks, many a times the "how to do this" is not that descriptive. thanx – Arifah Azhar Jan 6 '12 at 9:16
up vote 9 down vote accepted

To use the command \url you need to load the url package by adding \usepackage{url} to your preamble.

Many packages (like hyperref) load url automatically.

share|improve this answer
thanx a bunch :) – Arifah Azhar Jan 6 '12 at 9:14

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