Of course, these results are evident, if
one uses the Conway-Schneeberger Fifteen Theorem [2], as the author
also mentioned, however it is interesting to give a direct proof for some
specific quadratic forms based on simple argument. It is the purpose
of this short note to prove five of the seven quadratic forms mentioned
and proven by Deutsch, using the universality of the classical quadratic
form associated to the celebrated Lagrange’s Theorem of Four Squares
and Euler’s trick