摘要
In this paper, Π denotes Krein space, (·,·) denotes the infinitive inner product. The Π-type spaces refer to the Pontrjagin spaces or Krein spaces. The Hilbert spaces are also regarded as Π-type spaces. The chief aim of this paper is to discuss the structure of the Π space. Definition 1. Let L be a closed subspace of Π. L is called a complete subspaee of Π if it is also a Π-type space according to (·,·).
