Sentence:  Very recently , observations have been made at 8 - <WSD>mm</WSD> wave length with a reflector 22 meters in diameter with a resultant beam width of only about 2 ' ( Amenitskii , Noskova , and Salomonovich , 1960 ) . 
Meaning of the word marked with <WSD> tags:  a metric unit of length equal to one thousandth of a meter