The bright star Capella is an excellent illustration of these spectroscopic binaries.
"A Text-Book of Astronomy"
George C. Comstock
In binaries the bonds of each element must balance.
"An Introduction to Chemical Science"
R.P. Williams
All double stars are not binaries; many of them are known as 'optical doubles'-an impression created by two stars when almost in the same line of vision, and, though apparently near, are situated at a great distance apart and devoid of any physical relationship.
"The Astronomy of Milton's 'Paradise Lost'"
Thomas Orchard