This work is attributed to John Smith = we think John Smith did this.
The attribution of the work was done by a panel of experts on the works of John Smith (attribution being the process of deciding who to attribute something to)
Official means something that has been approved at a higher level for routine use for example, the official textbook for the course is the one that has been approved by the exam board. An official statement on the news is one that has been prepared in advance, it's not just an off-hand comment. Officer is a job title and the person holds an official role and has certain duties to comply with. Examples include Police Officer, Parking Officer. A company may have a Health and Safety Officer etc.