The semi colon is not necesary in this sentence.
It often reflects that it's not yours but someone else's
Law
Example:
<span>PV = k
Where P is pressure of the gas and V is volume of the gas and k is constant.
It easily derived by the equation above.
Boyle’s law states that when the gas amount and its temperature the same or held constant, within a closed system, the relation of the pressure exerted by the gas is inversely proportional to its volume. So in the situation, the pressure increases, so its volume decreases.</span>
<span>the cook-voyage collections at oxford, 1772−2015 - University of Oxford</span>