551 us8970842b2 pdf cache all wpfb_file_category citations 1425538323 88e21cbc32c2a9bb009633f34690e7b2 4b7c5872c891739fe8e3632aa03a32f10f6cca9f22c0e73a7e61aed3bbf5b548 us patent 8 970 842 b2 multi harmonic inline reference cell for optical trace gas sensing 2015 03 05 07 52 0 66 249 75 224 2020 01 23 11 25 1528055060 pdf application num_pages analyze pdf_pages pdf_2text timings
