A variety of scenarios was proposed to explain the tracks.
Several different theories have been proposed to explain the origins of this name.
A number of mechanisms have been proposed to explain this effect.
Two main theories have been proposed to explain the development of the disorder.
Various theories have been proposed to explain how the Moon formed.
A possible companion has been proposed to explain the slow rotation.
Several reasons have been proposed to explain some of this discrepancy.
Several theories have been proposed to explain social support's link to health.
Two major theories have been proposed to explain how this process of integration takes place.
Various reasons have been proposed to explain why the car performed so poorly.
