EASA mandated a minimum number of training sessions in AMC1 FCL.740(b)(1) which is duplicated at the end of Standards Document 14(A).
'Training as required' was an AltMoC submitted by the UK CAA as a pragmatic solution to the requirements in AMC1 FCL.740 (b)(1) following feedback from industry. The CAA AltMoC can be found in CAP 804 Section 4 Part H Subpart 1 page 7. There is a similar AltMoC for Instrument Rating refresher training sessions required by AMC1 FCL.625(c)(1) in CAP 804 Section 4 Part G Subpart 1 page 4.
It's listed on the EASA website at page 3 of this document as a current AltMoC (EASA AltMoC reference 2014‐00006):
https://www.easa.europa.eu/download/...st-for-web.pdf
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