Spatial crowdsourcing is an effective and novel method. In crowdsourcing systems. a centralized platform is traditionally used to allocate tasks and select workers. Centralized platforms always face following challenges: 1) How to ensure the rationality of tasks allocating; 2) How to ensure the payments of workers in the system when dishonest requesters exist; 3) How to ensure the max... https://www.lockdownsecuritycanada.shop/product-category/coaxial-speakers/