Disagreements in published boiling temperatures of tin, gallium etc.

[Peter Dow]

I have noted big disagreements of a scale of hundreds of degrees centigrade in published values for the boiling temperature of chemical elements such as tin and gallium.

For example,

Tin
Wikipedia (http://en.wikipedia.org/wiki/Tin) - 2602 °C, 2875 K, 
Chemical Elements website (http://www.chemicalelements.com/elements/sn.html) - 2270.0°C, 2543.15 K
which agrees with one of my text books
Penguin Dictionary of Chemistry - 2270°C
but not the other
Chemistry, Molecules, Matter and Change - 2720°C


Gallium
Wikipedia (http://en.wikipedia.org/wiki/Gallium) - 2204 °C, 2477 K, 
Chemical Elements website (http://www.chemicalelements.com/elements/ga.html) 2403.0 °C, 2676.15 K
which agrees with one of my text books
Penguin Dictionary of Chemistry - 2403 °C
but not the other
Chemistry, Molecules, Matter and Change - 2070 °C


Of course I am wondering why the different values - errors by the authors of books or websites or genuine disagreements between scientists as to the values?

Which source do people recommend as the most reliable source of accurate boiling temperature information and why?

[Borek]

I can't tell you what is the best source, what I can tell you is that such discrepancies are nothing unusual. Sometimes they can be traced down to separate sources that originally published different values of something. If I recall correctly that's the case with density tables of the sulfuric acid - they come in two flavors, and I have seen both versions printed already in books from before IWW. All later ones where just reprints.