It is a great convenience to be able to reference expressions, or parts of expressions, created in Maple. The following examples show how this might be done in a few specific instances. Giving an expression a name greatly simplifies such references. Alternatively, the auto-generated equation labels often serve in lieu of an explicitly assigned name. In desperation, it is always possible to copy/paste or select-and-drag to move something from one place on the screen to another. The process of selecting and dragging is equivalent to the cut/paste operation; to achieve a copy/paste interactively, hold down the Control key (Windows, with equivalents on other operating systems) and drag. This operation is consistently called "Control-drag" throughout this ebook.