sentences:  However, in January 1963 the Berezniak design bureau (which became MKB Raduga in 1967) was tasked with developing such a missile as part of the K-28P weapon complex based around a 'Wild Weasel' version of the Yak-28 'Brewer' bomber (hence -28; the 'K' stands for kompleks, P stands for protivradiolokatsyonny 'anti-radar').The main difficulty came in the design of the APR-28 guidance system undertaken by CKB-111 (later NPO Avtomatika).This meant that the Kh-28 missile was not ready until the 1970s.