TITLE: Introductory text for calculus of variations
QUESTION [35 upvotes]: I am currently working on problems that require familiarity with calculus of variations. I am fairly new to this field. Please suggest a good introductory book for the same that could help me pick up the concepts quickly.
edit:
I would prefer books which are available in PDF format online.

REPLY [2 votes]: One I really enjoy is Calculus of Variations by Jürgen Jost - he also has an awesome book on Partial Differential Equations!