Many of the victims' families fear that amid the talk of office space, building design, street grids, transit hubs and financing, their voices are becoming fainter.

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Mr Silverstein had brought in the second team of architects, having complained there was not enough office space in Mr Libeskind's winning design.

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Roughly one-third complete, it will boast 200 retailers, office space, a luxury hotel and apartment complexes with different levels of design, amenities and pricing to appeal to three different segments of the market.

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According to Mark Matney of Lockheed-Martin, who works at the Orbital Debris Programme Office at the Johnson Space Centre in Houston, Texas, shielding is an increasing influence on satellite design.

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