S-cool notes: Scroll down to the section on CPA
http://s-cool.co.uk/alevel/business-studies-as--a2-level/production-decision-making/scale-of-production.html
Tutor2u notes:
http://tutor2u.net/business/production/critical-path-analysis.htm
Bizhelp notes:
http://www.bizhelp24.com/small-business-portal/critical-path-analysis-3.html
Powerpoint:
http://www.businessstudiesonline.co.uk/AsA2BusinessStudies/TheoryNotes/2880/3Hr/PDF/05%20Critical%20Path%20Analysis.pdf