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Kekule made his classical proposal that the six carbon atoms of benzene were arranged in a hexagon.

It has been proposed (or speculated, or suggested) that a series of reactions is involved.

He suggested that there should be two gas diffusion terms.

Goldbach conjectured that every even number ...

He proposed that both attractive and repulsive forces could exist between atoms.

It is speculated that the oxygen resulted from the bombardment of the seas by certain wavelengths of ultraviolet light.

Scientists theorize that the planets in our solar system formed at ...

It was conjectured that the eukaryotes had eliminated the need for ... (биол.). The suggestion has been made that the underlying asthenosphere has an undulating upper surface.

He reasoned (or argued, or hypothesized) that erosion must be burying layers of sediment under ...

Источник: Русско-английский научно-технический словарь на Gufo.me