Chapter 28, page 15. Bottom of the page says - There are usually an infinite number of theoretical solutions to the equations, although there may be no real solution for the asset-maturity dates available. Not sure what is meant. Does it mean that if the solution (i.e. the asset allocation) suggests holding a percentage of assets in long dated bonds, they might not be available?
Yes that's broadly what it means: although a little more specifically: a solution might require you to invest in a bond with an outstanding duration of, say, 11 years and 126 days and such a bond might not be available.
