1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S
1993A&A...273..533S