Compared efficiency of different spaced-repetition memorisation techniques
A quick Pubmed search shows a couple of potential useful papers. The more promising:


Karpicke, JD., &amp; Bauernschmidt, A. (2011) Spaced retrieval: absolute spacing enhances learning regardless of relative spacing J Exp Psychol Learn Mem Cogn. 37(5):1250-7
Toppino, TC., Kasserman, JE., &amp; Mracek WA. (1991) The effect of spacing repetitions on the recognition memory of young children and adults J Exp Child Psychol. 51(1):123-38.