His foundation-laying "Die mathematischen und physikalischen Theorieen der höheren Geodäsie, 1. Teil" was published in Leipzig, 1880. This book can be retrieved page by page from the attached directory Helmert1880. The extremely fast semi-analytic solution of Helmert's method was first reported by Wolf (1978). The covariance matrix of estimated parameters was reported in Lange (1982) “Multipath propagation of VLF Omega signals”, IEEE PLANS '82 - Position Location and Navigation Symposium Record, December 1982, see pages 302-309 (308). The Helmert-Wolf blocking (HWB) solution is intensively exploited by European, US and Canadian geodesists in modern GPS applications.