Useful article for discussion on factors affecting supply, see where to find the relevant section within the specification for A Level Economics:

Edexcel spec reference 1.2.4 b) The factors that may cause a shift in the supply curve (the conditions of supply)

AQA spec reference The determinants of the supply of goods and services 

OCR spec reference P8  Explain, with the aid of a diagram, how changes in the factors affecting supply will impact on equilibrium price and quantity