A referencing "escape room" puzzle

I did a talk the other day for my University which ended up using elements of escape room stuff.
One of the puzzles I used was based around building references.

 

 

pack of material tied up with rubber band

 There was a pack of material for each group tied up with a rubber band.

A guide and 3 packs of cards

When unwrapped, they found a "Quick guide to referencing" and 3 small packs of cards and a post-it with each.

One of the packs unwrapped

 When each small pack was unwrapped it contained a set of components for a reference, the type of reference to build (book or journal article) and a number (in this case 1).

A reference made with the cards

 If they made up the references correctly, they could then reveal a simple puzzle on the other side of the cards, like below. It only made sense when the cards were in the correct order.

A puzzle revealed

The 3 packs of cards gave a 3 digit number which opened the next padlock / box!