Tense: Use the present tense unless there is overwhelming needs to use something else. If
necessary, you can say "others have shown"; you should not say "others showed".
Mood: Use indicative instead of imperative ("x" instead of "note that x" or "recall that x"),
which forces the reader to take some action. "x" actually turns out to be stronger in most cases.
Also, avoid "would"; "is" is usually better.