Mordell: https://www.maths.ed.ac.uk/~v1ranick/papers/mordell4.pdf
Elkies: http://people.math.harvard.edu/~elkies/Misc/E8.pdf,
Characterisation of lattice: https://arxiv.org/pdf/math/9906019.pdf
Mordell: https://www.maths.ed.ac.uk/~v1ranick/papers/mordell4.pdf
Elkies: http://people.math.harvard.edu/~elkies/Misc/E8.pdf,
Characterisation of lattice: https://arxiv.org/pdf/math/9906019.pdf