Data Sources

Physical constants
NIST Physics Laboratory - Constants, units and uncertainty
Atomic and isotope mass
NIST Physics Laboratory - Atomic weights and isotope composition
Atomic density
ILL Neutron Data Booklet
Covalent Radii
Cordero, et al., Dalton Trans., 2008, 2832-2838, doi:10.1039/801115j
Magnetic form factors
Brown. P. J., In International Tables for Crystallography, Volume C, Wilson. A. J. C (ed), section 4.4.5
Neutron scattering factors
Atomic Institute for Austrian Universities
X-ray scattering factors
Center for X-Ray Optics
Neutron activation

IAEA (1987) Handbook on Nuclear Activation Data. TR 273 (International Atomic Energy Agency, Vienna, Austria, 1987).

Shleien, B., Slaback, L.A., Birky, B.K., (1998). Handbook of health physics and radiological health. Williams & Wilkins, Baltimore.

Crystal structure
Ashcroft and Mermin
Oxidation states

wikipedia: List of oxidation states of the elements

Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements, 2nd ed. Butterworth-Heinemann. pp. 27–28. ISBN 0-08-037941-9.

FASTA and biomolecule formulas
Perkins (1988), Modern Physical Methods in Biochemistry Part B, 143-265.