Latex Special Character/Font problem

I am new to LaTeX, which I am trying to write my thesis with.

Can anybody guide me how to write

?开发者_高级运维 or maybe it is a special font?

Thank you.

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It is the calligraphic form of L. You call it as \mathcal{L} inside a math environment.

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When in doubt, try http://detexify.kirelabs.org/classify.html.