1. The direct sum of Banach spaces with respect to a basis;Davis, William J.;Studia Math.,1966
2. An example of a non-shrinking basis;Pełczyński, A.;Rev. Roumaine Math. Pures Appl.,1965
3. Shrinking bases in Banach spaces;Retherford, J. R.;Amer. Math. Monthly,1966
4. The basis in Banach space;Wilansky, Albert;Duke Math. J.,1951