With Character Map, you can select a large range of non-standard and international characters to put in your documents.
Menu: Accessories > Character Map
- Choose from many different international categories
- Includes support for the phonetic alphabet
- Part of the default Ubuntu installation
Hints and Tips
View >By Unicode Block can make it a lot easier to find mathematical symbols.
- Search find dialog is also quite useful if you want to copy a particular symbol as well and searches over the names.
Other applications you may wish to look at
Character Palette applet
ComposeKey direct entry by typing multiple keystrokes