Science. 1972 Jul 21;177(4045):261-3. doi: 10.1126/science.177.4045.261.
Birch's law arises in the physics of solids as a linear approximation, in a certain range of density, of a power law. For a change of chemical composition within the same crystal structure, the velocity-density relation is constant with a slope of nearly -0.5 in the first-order approximation.
伯奇定律在固体物理学中是作为一种线性近似出现的，在一定的密度范围内，它是一种幂律。对于同一晶体结构内的化学成分变化，在一级近似下，速度-密度关系是恒定的，斜率接近-0.5。
