Classification of extraspecial p-groups using quadratic forms

Let p be a prime number. A p-group is said to be extraspecial p-group if its center, derived subgroup and Frattini subgroup all coincide and have order p. For every n ∈ N, there are exactly two extraspecial p-groups of order p2n+1 up to isomorphism and no extraspecial p-group of order p2n. This classification of extraspecial p-group is proved by using theory of quadratic forms and bilinear forms.