Whereas , in the case of products where European standards cannot be produced or foreseen within a reasonable period of time or of products which deviate substantially from a standard , the fitness for use of such products may be proved by recourse to European technical approvals on the basis of common guidelines; whereas the common guidelines for the granting of European technical approvals will be adopted on the basis of the interpretative documents.
The above sentence is very complicated. Please provide me a simplified synonymous version consisting of multiple sentences:
For products for which European standards are not drawn up within a reasonable period of time can or cannot be expected , or which deviate significantly from a standard , the usability can be confirmed with the aid of the European technical approval on the basis of common guidelines . The common guidelines for the granting of European technical approvals are being drawn up taking into account the basic documents .