on Mac OS X, there is a character palette, available under the Keyboard menu.
On Mac OS X you can also use "Unicode Hex Input" as your input method. To do so * launch System Preferences * choose "International" * choose the "Input Menu" tab * scroll down the list to "Unicode Hex Input" (which is very near the bottom) and check it * optional: check "Show input menu in menu bar" -- very helpful, as it shows you at a glance which input keyboard you are using, and using one while you think you're using another can be the source of significant confusion and thus frustration Now, while in oXygen or any other Unicode-aware editing environment, you can enter Unicode characters via their 4-digit (hexadecimal) code-points. To do so: * select "Unicode Hex Input" as the keyboard from the keyboard menu (often shows up as a national flag) * type the four hex digits while holding down OPTION. E.g., opt-0 opt-3 opt-C opt-0 inserts a GREEK SMALL LETTER PI.