Recently, I was asked about citing the bubble and tower shields, and I did not have the appropriate references readily to hand at the time. I’m still tracking some of them down. Both types of Shielding _are_ mentioned in chapter XVIII of Dion Fortune’s _Psychic Self Defence_ book, of 1929. There is a PDF form of the book floating around. It’s found at http://jricher.com/occult/psychic.pdf for example, on page 88, I think.
The bubble is found more often in basic psionic, psychic, and magic literature than the tower shield.