I found it in the Flash MX 2004 Help:


To include multilanguage text using an externally loaded file:
In the Flash authoring tool, create a dynamic or input text field to display the text in the document. For more information, see Working with Text.
In the Property inspector, with the text field selected, assign an instance name to the text field.
Create a text or XML file that defines the value for the text filed variable.
Save the file in UTF-8 (recommended), UTF-16BE, or UTF-16LE format.
If you are using UTF-16 format, make sure a byte order mark is included at the beginning of the file to identify the encoding:

For UTF-16BE, the first byte of the file should be OxFE, and the second byte should be OxFF.
For UTF-16LE, the first byte of the file should be OxFF, and the second byte should be OxFE.
Note: Most text editors that can save files in UTF-16BE or LE automatically add the BOMs to the files.

Use one of the following ActionScript procedures to reference the external file and load it into the dynamic or input text field:
Use the loadVariables action to load an external file. For more information, see loadVariables().
Use the getURL action to load an external file from a specified URL. For more information, see getURL().
Use the LoadVars object (a predefined client-server object) to load an external text file from a specified URL. For more information, see LoadVars class.
Use the XML object (a predefined client-server object) to load an external XML file from a specified URL. For more information, see XML class.