After entering opposition territory, it was monitored by Russian drones, which was recognized by the Russian Defense Ministry, which also provided accurate GPS coordinates of the route to be taken and the target in accordance with the agreement with Syrian officials. Similar agreements followed with Britain, France and Russia, as well as a defence agreement with other Gulf countries. In 2005, Bougainville voters elected their own parliament, according to an agreement reached in 2003. Under the agreement with the Air Force, biomedical research cannot be carried out on animals. For example, the quantities of mineral and organic fertilizers and the corresponding application periods were adjusted as inputs into the model based on measures obtained by farmers in accordance with the agreement with TTV, as explained above. Under the previous agreement, Hero Honda was not allowed to export bicycles. [mydigitalfc.com] He then stated: „Transfer 10% of the amount I managed to get from DS and DG, in accordance with my agreement with carson [sic] … HSBC account in the UK.“ Per means after, so you can indeed say „after our agreement, you must… ». The one as in your first sentence is pleonastic, and sounds affected: I would avoid it.
The very common „as usual“ is a humorous prolixity. The show will arrive first before December, in accordance with our agreement. Finally, in accordance with the agreements of the Treaty of Paris (1763), the British withdrew. In English, we use `after… To quote someone else. To self-quote is clearly absurd, unless you cite a document you have published or something you have written formally. Quoting your opinion or knowledge makes no sense. People who want to look important write as pro. People who are important write. I suggest that the reason „As per“ is particularly common in Indian publications is that Indian English is very much outside the language of Colonial Service administrators who, especially in the Victorian era, were very much in favour of this jargon.
As per is particularly common in Indian publications. It cannot be explained. Outside of India, attentive writers tend to avoid it so because it has a jargonist tone, and simply in tune with or as usual seems more natural.