  Explicit separable density matrices, for mixed two qubits states, are derived
by the use of Hilbert Schmidt decompositions and Peres Horodecki criterion. A
strongly separable two qubits mixed state is defined by multiplications of two
density matrices given with pure states while weakly separable two qubits state
is defined by multiplications of two density matrices which includes non-pure
states. We find the sufficient and necessary condition for separability of
two-qubits density matrices and show that under this condition the two-qubit
density matrices are strongly separable.
