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<div class="subtitle">Description</div>

<p>
<code>amu</code> returns the SI value in kg of 1 amu, the atomic mass constant,
in <code>value</code> and the standard deviation in <code>sigma</code> (if two output arguments are specified).
</p>

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<div class="subtitle">Reference</div>

<p>
The value and the standard deviation are taken from the 2022 CODATA collection of re