The Air Operations Regulation contains implementing rules which must be complied with.
In addition, there are acceptable means of compliance (AMCs) published by EASA. The AMCs give more detail regarding the implementing rules and they demonstrate an acceptable means of compliance.
When an operator uses the AMC then there is a presumption of compliance with the rule. However, an operator may develop an alternative means of compliance; they must still fully meet the requirements of the implementing rules, but by way of an alternative means or procedure set out in the operations manual.
As part of the declaration you must state whether or not you use any alternative means of compliance. If you do, you must then state a reference to those published AMCs for which you are using an alternative means of compliance. You do not need to submit the alternative text.