  This paper also has excessove overlap with the following papers also written
by the authors or their collaborators: gr-qc/0502060, gr-qc/0606028,
gr-qc/0511095, gr-qc/0505078, gr-qc/0603044, gr-qc/0608014, gr-qc/0510123,
gr-qc/0607109, gr-qc/0602012, and others.
