reference numbers reference numbers are used reference numerals reference object reference objects reference of the committee reference offer reference one reference only reference oscillator reference other reference page reference pages reference paper reference part reference partner reference path reference pattern reference period reference periods reference person reference phase reference photo reference photos reference picture reference pictures reference pixel reference pixels reference plane reference plate reference platform reference point reference points reference population reference position reference potential reference power reference pressure reference price reference prices reference product reference products reference profile reference project reference projects reference publication reference publications reference purposes reference purposes only reference quantity reference questions reference range reference ranges reference rate reference rates reference report reference room reference salary reference sample reference samples reference scale reference scenario reference section reference sensor reference sequence reference sequences reference series reference service reference services reference set reference shall be made reference shareholder reference sheet reference should reference should be made reference sign reference signal reference signals reference signature reference signs reference signs in reference site reference sites reference size reference software reference solution reference solutions reference source reference sources reference spectrum reference speed reference standard reference standards reference state reference station reference stations reference steel reference strain reference strains