Unity element 1 [duplicate]

Possible Duplicate:
How to look up a symbol?

I'd like to write the unity element 1 in LaTeX. I have tried these methods:

$\mathbbm{1}$ \\
$\mathbb{1}$\\
$\mathbbss{1}$\\
$\mathbbtt{1}$\\
$\mathds{1}$\\

but I receive the integer 1. I think that I'm missing a suitable package. How to solve this problem?

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Does this help?: douglas.stebila.ca/blog/archives/2004/06/27/… –  Jellby Jul 5 '12 at 10:59
If you load the package bbold, you can type \mathbb{1} (in math-mode, of course) to get what you want. The "standard" blackboard bold glyphs are available only for uppercase letters -- hence the need to load an extra package. –  Mico Jul 5 '12 at 10:59
@Mico I believe you have answered the question. I recommend you post your comment as an answer. –  azetina Jul 5 '12 at 14:34
@azetina: done! –  Mico Jul 5 '12 at 15:25