Measure for Measure and Songs of Innocence & Experience both form part of the paper which examines Module 4, 'Texts in Time'. The entry code for this paper is LTA4.
The study of First World War literature comes under Module 6, 'Reading for Meaning'. As you've stated, the entry code is LTA6.
You will also be assessed on Module 5, 'Literary Connections', either by coursework or with a written examination. The entry code for the coursework component is LA5C. If the written examination is taken, the code is LA5W.
This information is derived from reading paragraph 3.3 and Sections 13, 14 & 15, here:
http://www.aqa.org.uk/qual/pdf/AQA-5741-6741-W -SP-07.PDF
Please check that I've identified the correct examination and entry codes. I wouldn't want to be responsible for you filling in the wrong information on an important form!
Chris