Nevertheless, the time information also introduces problems in cases where the writer goes back and forth over the page. The most common example is putting the dot on a letter i or j, or the horizontal bar of a lower-case letter t. Such an action can be performed either immediately after writing a letter or can be delayed to a later moment. There are different strategies. Some writers produce the dots after finishing a word while others finish a complete sentence or even paragraph of text before producing the delayed strokes for dots and bars. Whereas the optical result may appear impeccable, an on-line handwriting recognition system must attribute each delayed stroke to the correct character in the production sequence.