1. How do you value a brand?
The Brands and Branding section of the Warc Topics Index includes a category entitled "Brands Value and Purpose".
The search below on Business Source Complete will yield excellent information on the topic as well. Here we are searching for the term(s) brand, branding, or brands in the abstract or summary of the article. A variation in the endings of that term is requested by using the *. We then combine that term with EITHER value or valuation (again using the asterisk to search for any ending variation of valu--, or the term ROI (return on investment). In this example, the term "brand"and then either the term "valu*" or "ROI" must show up in the abstract as well.
2. What is the halo effect of a brand in a brand extension?
Searching in the library database Business Source Complete is a good choice. The term "halo effect" is actually a subject term in this database. Combining this term (in the subject field) with the truncated term brand* (for brands, branding or brand), will yield targeted and precise results.
Brand (brand name) A tradename used to identify a specific product, manufacturer, or distributor. The sale of most branded products began in the UK at the turn of the century; some, such as Bovril (Trademark) and Horlicks (Trademark), were mid-Victorian, introduced when manufacturers wanted to distinguish their goods from those of their competitors. As consumers became more sophisticated, manufacturers placed more emphasis upon promoting their brands directly to consumers (rather than to distributors), spending considerable sums on advertising the high quality of their products. Manufacturers believe that if they invest in the quality of their brands they will build up a brand image, to which consumers will respond by asking for their goods by their brand names and by being willing to pay a premium for them .
"Brand" A Dictionary of Business and Management. Ed. Jonathan Law. Oxford University Press, 2009. Oxford Reference Online. Oxford University Press.